use prolog::heap_print::*;
use prolog::machine::*;
use prolog::machine::compile::*;
use prolog::machine::machine_errors::*;
use prolog::machine::machine_indices::*;
use prolog::machine::toplevel::*;

use std::collections::HashSet;
use std::mem::swap;
use std::ops::{Range, RangeFrom};

pub struct TestOutputter {
    results: Vec<HashSet<String>>,
    contents: HashSet<String>,
    focus: String
}

impl TestOutputter {
    fn cache(&mut self) {
        self.begin_new_var();

        let mut contents = HashSet::new();
        swap(&mut contents, &mut self.contents);

        self.results.push(contents);
    }
}

impl HCValueOutputter for TestOutputter {
    type Output = Vec<HashSet<String>>;

    fn new() -> Self {
        TestOutputter { results: vec![],
                        contents: HashSet::new(),
                        focus: String::new() }
    }

    fn append(&mut self, focus: &str) {
        self.focus += focus;
    }

    fn push_char(&mut self, c: char) {
        self.focus.push(c);
    }

    fn begin_new_var(&mut self) {
        if !self.focus.is_empty() {
            let mut focus = String::new();
            swap(&mut focus, &mut self.focus);

            self.contents.insert(focus);
        }
    }

    fn insert(&mut self, idx: usize, c: char) {
        self.focus.insert(idx, c);
    }

    fn result(self) -> Self::Output {
        self.results
    }

    fn ends_with(&self, s: &str) -> bool {
        self.focus.ends_with(s)
    }

    fn len(&self) -> usize {
        self.focus.len()
    }

    fn truncate(&mut self, len: usize) {
        self.focus.truncate(len);
    }

    fn range(&self, index: Range<usize>) -> &str {
        &self.focus.as_str()[index]
    }

    fn range_from(&self, index: RangeFrom<usize>) -> &str {
        &self.focus.as_str()[index]
    }
}

pub fn collect_test_output(wam: &mut Machine, alloc_locs: AllocVarDict, mut heap_locs: HeapVarDict)
                           -> Vec<HashSet<String>>
{
    let mut output = TestOutputter::new();

    output = wam.test_heap_view(&heap_locs, output);
    output.cache();

    while let EvalSession::SubsequentQuerySuccess = wam.continue_query(&alloc_locs, &mut heap_locs)
    {
        output = wam.test_heap_view(&heap_locs, output);
        output.cache();
    }

    output.result()
}

pub fn collect_test_output_with_limit(wam: &mut Machine, alloc_locs: AllocVarDict,
                                      mut heap_locs: HeapVarDict, limit: usize)
                                      -> Vec<HashSet<String>>
{
    let mut output = TestOutputter::new();

    output = wam.test_heap_view(&heap_locs, output);
    output.cache();

    let mut count  = 1;

    if count == limit {
        return output.result();
    }

    while let EvalSession::SubsequentQuerySuccess = wam.continue_query(&alloc_locs, &mut heap_locs)
    {
        output = wam.test_heap_view(&heap_locs, output);
        output.cache();

        count += 1;

        if count == limit {
            break;
        }
    }

    output.result()
}

#[allow(dead_code)]
pub fn submit(wam: &mut Machine, buffer: &str) -> bool
{
    wam.reset();

    match compile_user_module(wam, buffer.as_bytes()) {
        EvalSession::InitialQuerySuccess(_, _) |
        EvalSession::EntrySuccess |
        EvalSession::SubsequentQuerySuccess =>
            true,
        _ => false
    }
}

#[allow(dead_code)]
pub fn submit_query(wam: &mut Machine, buffer: &str, result: Vec<HashSet<String>>) -> bool
{
    wam.reset();

    match string_to_toplevel(buffer.as_bytes(), wam) {
        Ok(term) =>
            match compile_term(wam, term) {
                EvalSession::InitialQuerySuccess(alloc_locs, heap_locs) =>
                    result == collect_test_output(wam, alloc_locs, heap_locs),
                EvalSession::EntrySuccess => true,
                _ => false
            },
        Err(_) => panic!("syntax error")
    }
}

#[allow(dead_code)]
pub fn submit_query_without_results(wam: &mut Machine, buffer: &str) -> bool
{
    wam.reset();

    match string_to_toplevel(buffer.as_bytes(), wam) {
        Ok(term) =>
            match compile_term(wam, term) {
                EvalSession::InitialQuerySuccess(..)
              | EvalSession::EntrySuccess => true,
                _ => false
            },
        Err(_) => panic!("syntax error")
    }
}

#[allow(dead_code)]
pub fn submit_query_with_limit(wam: &mut Machine, buffer: &str,
                               result: Vec<HashSet<String>>, limit: usize)
                               -> bool
{
    wam.reset();

    match string_to_toplevel(buffer.as_bytes(), wam) {
        Ok(term) =>
            match compile_term(wam, term) {
                EvalSession::InitialQuerySuccess(alloc_locs, heap_locs) =>
                    result == collect_test_output_with_limit(wam, alloc_locs,
                                                             heap_locs, limit),
                EvalSession::EntrySuccess => true,
                _ => false
            },
        Err(_) => panic!("syntax_error")
    }
}

#[allow(unused_macros)]
macro_rules! expand_strs {
    ($arr:expr) => (
        $arr.into_iter().map(|s| String::from(*s)).collect()
    )
}

#[allow(unused_macros)]
macro_rules! assert_prolog_success_with_limit {
    ($wam:expr, $buf:expr, [$($res:expr),*], $limit:expr) => (
        assert!(submit_query_with_limit($wam, $buf, vec![$(expand_strs!($res)),*], $limit))
    )
}

#[allow(unused_macros)]
macro_rules! assert_prolog_failure {
    ($wam: expr, $buf: expr) => (
        assert_eq!(submit_query_without_results($wam, $buf), false)
    )
}

#[allow(unused_macros)]
macro_rules! assert_prolog_success {
    ($wam:expr, $query:expr, [$($res:expr),*]) => (
        assert!(submit_query($wam, $query, vec![$(expand_strs!($res)),*]))
    );
    ($wam:expr, $buf:expr) => (
        assert_eq!(submit_query_without_results($wam, $buf), true)
    )
}

#[test]
fn test_queries_on_facts()
{
    let mut wam = Machine::new();

    submit(&mut wam, "p(Z, Z).");
    submit(&mut wam, "clouds(are, nice).");

    assert_prolog_success!(&mut wam, "?- p(Z, Z).", [["Z = _0"]]);
    assert_prolog_success!(&mut wam, "?- p(Z, z).", [["Z = z"]]);
    assert_prolog_success!(&mut wam, "?- p(Z, w).", [["Z = w"]]);

    assert_prolog_failure!(&mut wam, "?- p(z, w).");

    assert_prolog_success!(&mut wam, "?- p(w, w).");

    assert_prolog_failure!(&mut wam, "?- clouds(Z, Z).");

    assert_prolog_success!(&mut wam, "?- clouds(are, Z).", [["Z = nice"]]);
    assert_prolog_success!(&mut wam, "?- clouds(Z, nice).", [["Z = are"]]);

    submit(&mut wam, "p(Z, h(Z, W), f(W)).");

    assert_prolog_failure!(&mut wam, "?- p(z, h(z, z), f(w)).");
    assert_prolog_success!(&mut wam, "?- p(z, h(z, w), f(w)).");
    assert_prolog_success!(&mut wam, "?- p(z, h(z, W), f(w)).", [["W = w"]]);
    assert_prolog_success!(&mut wam, "?- p(Z, h(Z, w), f(Z)).", [["Z = w"]]);
    assert_prolog_failure!(&mut wam, "?- p(z, h(Z, w), f(Z)).");

    submit(&mut wam, "p(f(X), h(Y, f(a)), Y).");

    assert_prolog_success!(&mut wam, "?- p(Z, h(Z, W), f(W)).", [["W = f(a)", "Z = f(f(a))"]]);
}

#[test]
fn test_queries_on_rules() {
    let mut wam = Machine::new();

    submit(&mut wam, "p(X, Y) :- q(X, Z), r(Z, Y).");
    submit(&mut wam, "q(q, s).");
    submit(&mut wam, "r(s, t).");

    assert_prolog_success!(&mut wam, "?- p(X, Y).", [["Y = t", "X = q"]]);
    assert_prolog_success!(&mut wam, "?- p(q, t).");
    assert_prolog_failure!(&mut wam, "?- p(t, q).");
    assert_prolog_success!(&mut wam, "?- p(q, T).", [["T = t"]]);
    assert_prolog_failure!(&mut wam, "?- p(t, t).");

    submit(&mut wam, "p(X, Y) :- q(f(f(X)), R), r(S, T).");
    submit(&mut wam, "q(f(f(X)), r).");

    assert_prolog_success!(&mut wam, "?- p(X, Y).", [["X = _0", "Y = _1"]]);

    submit(&mut wam, "q(f(f(x)), r).");

    assert_prolog_success!(&mut wam, "?- p(X, Y).", [["X = x", "Y = _1"]]);

    submit(&mut wam, "p(X, Y) :- q(X, Y), r(X, Y).");
    submit(&mut wam, "q(s, t).");
    submit(&mut wam, "r(X, Y) :- r(a).");
    submit(&mut wam, "r(a).");

    assert_prolog_success!(&mut wam, "?- p(X, Y).", [["X = s", "Y = t"]]);
    assert_prolog_failure!(&mut wam, "?- p(t, S).");
    assert_prolog_success!(&mut wam, "?- p(s, T).", [["T = t"]]);
    assert_prolog_success!(&mut wam, "?- p(S, t).", [["S = s"]]);

    submit(&mut wam, "p(f(f(a), g(b), X), g(b), h) :- q(X, Y).");
    submit(&mut wam, "q(X, Y).");

    assert_prolog_success!(&mut wam,  "?- p(f(X, Y, Z), g(b), h).",
                           [["Z = _3", "Y = g(b)", "X = f(a)"]]);
    assert_prolog_failure!(&mut wam, "?- p(f(X, g(Y), Z), g(Z), X).");
    assert_prolog_success!(&mut wam, "?- p(f(X, g(Y), Z), g(Z), h).",
                           [["Z = b", "Y = b", "X = f(a)"]]);
    assert_prolog_success!(&mut wam, "?- p(Z, Y, X).",
                           [["X = h", "Y = g(b)", "Z = f(f(a), g(b), _7)"]]);
    assert_prolog_success!(&mut wam, "?- p(f(X, Y, Z), Y, h).",
                           [["Y = g(b)", "Z = _3", "X = f(a)"]]);

    submit(&mut wam, "p(_, f(_, Y, _)) :- h(Y).");
    submit(&mut wam, "h(y).");

    assert_prolog_success!(&mut wam, "?- p(_, f(_, Y, _)).", [["Y = y"]]);
    assert_prolog_success!(&mut wam, "?- p(_, f(_, y, _)).");
    assert_prolog_failure!(&mut wam, "?- p(_, f(_, z, _)).");
}

#[test]
fn test_queries_on_predicates() {
    let mut wam = Machine::new();

    submit(&mut wam, "p(X, a). p(b, X).");

    assert_prolog_success!(&mut wam, "?- p(x, Y).", [["Y = a"]]);
    assert_prolog_success!(&mut wam, "?- p(X, a).", [["X = _0"],  // 1st case
                                                     ["X = b"]]); // 2nd case.
    assert_prolog_success!(&mut wam, "?- p(b, X).", [["X = a"],  // 1st case
                                                     ["X = _0"]]); // 2nd case.
    assert_prolog_success!(&mut wam, "?- p(X, X).", [["X = a"],
                                                     ["X = b"]]);
    assert_prolog_success!(&mut wam, "?- p(b, a).");
    assert_prolog_failure!(&mut wam, "?- p(a, b).");

    submit(&mut wam, "p(X, Y, a). p(X, a, Y). p(X, Y, a).");

    assert_prolog_success!(&mut wam, "?- p(c, d, X).", [["X = a"],
                                                        ["X = a"]]);
    assert_prolog_success!(&mut wam, "?- p(a, a, a).");
    assert_prolog_failure!(&mut wam, "?- p(b, c, d).");

    submit(&mut wam, "p(X, a). p(X, Y) :- q(Z), p(X, X).");

    assert_prolog_success!(&mut wam, "?- p(X, Y).", [["X = _0", "Y = a"]]);
    assert_prolog_success!(&mut wam, "?- p(x, a).");
    assert_prolog_success!(&mut wam, "?- p(X, a).", [["X = _0"]]);
    assert_prolog_failure!(&mut wam, "?- p(X, b).");

    submit(&mut wam, "q(z).");

    assert_prolog_success_with_limit!(&mut wam, "?- p(X, b).", [["X = a"],
                                                                ["X = a"],
                                                                ["X = a"]],
                                      3);
    assert_prolog_success!(&mut wam, "?- p(x, a).");
    assert_prolog_success_with_limit!(&mut wam, "?- p(X, Y).", [["X = _0", "Y = a"],
                                                                ["Y = _1", "X = a"],
                                                                ["Y = _1", "X = a"]],
                                      3);

    submit(&mut wam, "p(X, a). p(X, Y) :- q(Y), p(X, X).");

    assert_prolog_success_with_limit!(&mut wam, "?- p(X, Y).", [["X = _0", "Y = a"],
                                                                ["Y = z", "X = a"]],
                                      2);
    assert_prolog_failure!(&mut wam, "?- p(X, b).");

    submit(&mut wam, "p(a, z). p(X, Y) :- q(Y), p(X, Y).");

    assert_prolog_success_with_limit!(&mut wam, "?- p(X, Y).", [["X = a", "Y = z"],
                                                                ["X = a", "Y = z"]],
                                      2);

    assert_prolog_success_with_limit!(&mut wam, "?- p(X, z).", [["X = a"],
                                                                ["X = a"]],
                                      2);
    assert_prolog_success!(&mut wam, "?- p(a, z).");
    assert_prolog_success_with_limit!(&mut wam, "?- p(a, X).", [["X = z"],
                                                                ["X = z"]],
                                      2);
    assert_prolog_failure!(&mut wam, "?- p(b, a).");

    submit(&mut wam, "p(X, Y, Z) :- q(X), r(Y), s(Z).
                      p(a, b, Z) :- q(Z).");

    submit(&mut wam, "q(x).");
    submit(&mut wam, "r(y).");
    submit(&mut wam, "s(z).");

    assert_prolog_success!(&mut wam, "?- p(X, Y, Z).", [["Y = y", "X = x", "Z = z"],
                                                        ["Y = b", "X = a", "Z = x"]]);
    assert_prolog_failure!(&mut wam, "?- p(a, b, c).");
    assert_prolog_success!(&mut wam, "?- p(a, b, C).", [["C = x"]]);

    submit(&mut wam, "p(X) :- r(X).");
    submit(&mut wam, "r(X) :- s(X, t). r(X) :- t(X, u).");

    submit(&mut wam, "s(x, t).");
    submit(&mut wam, "t(y, u).");

    assert_prolog_success!(&mut wam, "?- p(X).", [["X = x"],
                                                  ["X = y"]]);
    assert_prolog_success!(&mut wam, "?- p(x).");
    assert_prolog_success!(&mut wam, "?- p(y).");
    assert_prolog_failure!(&mut wam, "?- p(z).");

    submit(&mut wam, "p(f(f(X)), h(W), Y) :- g(W), h(W), f(X).
                      p(X, Y, Z) :- h(Y), g(W), z(Z).");
    submit(&mut wam, "g(f(X)) :- z(X). g(X) :- h(X).");
    submit(&mut wam, "h(w). h(x). h(z).");
    submit(&mut wam, "f(s).");
    submit(&mut wam, "z(Z).");

    assert_prolog_success!(&mut wam, "?- p(X, Y, Z).", [["Y = h(w)", "X = f(f(s))", "Z = _2"],
                                                        ["Y = h(x)", "X = f(f(s))", "Z = _2"],
                                                        ["Y = h(z)", "X = f(f(s))", "Z = _2"],
                                                        ["Y = w", "Z = _2", "X = _0"],
                                                        ["Y = w", "Z = _2", "X = _0"],
                                                        ["Y = w", "Z = _2", "X = _0"],
                                                        ["Y = w", "Z = _2", "X = _0"],
                                                        ["Y = x", "Z = _2", "X = _0"],
                                                        ["Y = x", "Z = _2", "X = _0"],
                                                        ["Y = x", "Z = _2", "X = _0"],
                                                        ["Y = x", "Z = _2", "X = _0"],
                                                        ["Y = z", "Z = _2", "X = _0"],
                                                        ["Y = z", "Z = _2", "X = _0"],
                                                        ["Y = z", "Z = _2", "X = _0"],
                                                        ["Y = z", "Z = _2", "X = _0"]]);
    assert_prolog_success!(&mut wam, "?- p(X, X, Z).", [["Z = _1", "X = w"],
                                                        ["Z = _1", "X = w"],
                                                        ["Z = _1", "X = w"],
                                                        ["Z = _1", "X = w"],
                                                        ["Z = _1", "X = x"],
                                                        ["Z = _1", "X = x"],
                                                        ["Z = _1", "X = x"],
                                                        ["Z = _1", "X = x"],
                                                        ["Z = _1", "X = z"],
                                                        ["Z = _1", "X = z"],
                                                        ["Z = _1", "X = z"],
                                                        ["Z = _1", "X = z"]]);
    assert_prolog_success!(&mut wam, "?- p(f(f(Z)), Y, Z).", [["Y = h(w)", "Z = s"],
                                                              ["Y = h(x)", "Z = s"],
                                                              ["Y = h(z)", "Z = s"],
                                                              ["Y = w", "Z = _1"],
                                                              ["Y = w", "Z = _1"],
                                                              ["Y = w", "Z = _1"],
                                                              ["Y = w", "Z = _1"],
                                                              ["Y = x", "Z = _1"],
                                                              ["Y = x", "Z = _1"],
                                                              ["Y = x", "Z = _1"],
                                                              ["Y = x", "Z = _1"],
                                                              ["Y = z", "Z = _1"],
                                                              ["Y = z", "Z = _1"],
                                                              ["Y = z", "Z = _1"],
                                                              ["Y = z", "Z = _1"]]);
    assert_prolog_success!(&mut wam, "?- p(X, X, X).", [["X = w"],
                                                        ["X = w"],
                                                        ["X = w"],
                                                        ["X = w"],
                                                        ["X = x"],
                                                        ["X = x"],
                                                        ["X = x"],
                                                        ["X = x"],
                                                        ["X = z"],
                                                        ["X = z"],
                                                        ["X = z"],
                                                        ["X = z"]]);
    assert_prolog_success!(&mut wam, "?- p(X, Y, X).", [["Y = h(w)", "X = f(f(s))"],
                                                        ["Y = h(x)", "X = f(f(s))"],
                                                        ["Y = h(z)", "X = f(f(s))"],
                                                        ["Y = w", "X = _0"],
                                                        ["Y = w", "X = _0"],
                                                        ["Y = w", "X = _0"],
                                                        ["Y = w", "X = _0"],
                                                        ["Y = x", "X = _0"],
                                                        ["Y = x", "X = _0"],
                                                        ["Y = x", "X = _0"],
                                                        ["Y = x", "X = _0"],
                                                        ["Y = z", "X = _0"],
                                                        ["Y = z", "X = _0"],
                                                        ["Y = z", "X = _0"],
                                                        ["Y = z", "X = _0"]]);
    assert_prolog_failure!(&mut wam, "?- p(f(f(X)), h(f(X)), Y).");

    submit(&mut wam, "p(X) :- f(Y), g(Y), i(X, Y).");
    submit(&mut wam, "g(f(a)). g(f(b)). g(f(c)).");
    submit(&mut wam, "f(f(a)). f(f(b)). f(f(c)).");
    submit(&mut wam, "i(X, X).");

    assert_prolog_success!(&mut wam, "?- p(X).", [["X = f(a)"],
                                                  ["X = f(b)"],
                                                  ["X = f(c)"]]);

    submit(&mut wam, "p(X) :- f(f(Y)), g(Y, f(Y)), i(X, f(Y)).");
    submit(&mut wam, "g(Y, f(Y)) :- g(f(Y)).");

    assert_prolog_success!(&mut wam, "?- p(X).", [["X = f(a)"],
                                                  ["X = f(b)"],
                                                  ["X = f(c)"]]);
}

#[test]
fn test_queries_on_cuts() {
    let mut wam = Machine::new();

    // test shallow cuts.
    submit(&mut wam, "memberchk(X, [X|_]) :- !.
                      memberchk(X, [_|Xs]) :- memberchk(X, Xs).");

    assert_prolog_success!(&mut wam, "?- memberchk(X, [a,b,c]).", [["X = a"]]);
    assert_prolog_success!(&mut wam, "?- memberchk([X,X], [a,b,c,[d,e],[d,d]]).", [["X = d"]]);
    assert_prolog_success!(&mut wam, "?- memberchk([X,X], [a,b,c,[D,d],[e,e]]).", [["X = d", "D = d"]]);
    assert_prolog_failure!(&mut wam, "?- memberchk([X,X], [a,b,c,[e,d],[f,e]]).");
    assert_prolog_failure!(&mut wam, "?- memberchk([X,X,Y], [a,b,c,[e,d],[f,e]]).");
    assert_prolog_success!(&mut wam, "?- memberchk([X,X,Y], [a,b,c,[e,e,d],[f,e]]).", [["X = e", "Y = d"]]);

    // test deep cuts.
    submit(&mut wam, "commit :- a, !.");

    assert_prolog_failure!(&mut wam, "?- commit.");

    submit(&mut wam, "a.");

    assert_prolog_success!(&mut wam, "?- commit.");

    submit(&mut wam, "commit(X) :- a(X), !.");

    assert_prolog_failure!(&mut wam, "?- commit(X).");

    submit(&mut wam, "a(x).");

    assert_prolog_success!(&mut wam, "?- commit(X).", [["X = x"]]);

    submit(&mut wam, "a :- b, !, c. a :- d.");

    assert_prolog_failure!(&mut wam, "?- a.");

    submit(&mut wam, "b.");

    assert_prolog_failure!(&mut wam, "?- a.");

    submit(&mut wam, "d.");

    // we've committed to the first clause since the query on b
    // succeeds, so we expect failure here.
    assert_prolog_failure!(&mut wam, "?- a.");

    submit(&mut wam, "c.");

    assert_prolog_success!(&mut wam, "?- a.");

    submit(&mut wam, "a(X) :- b, !, c(X). a(X) :- d(X).");

    assert_prolog_failure!(&mut wam, "?- a(X).");

    submit(&mut wam, "c(c).");
    submit(&mut wam, "d(d).");

    assert_prolog_success!(&mut wam, "?- a(X).", [["X = c"]]);

    submit(&mut wam, "b.");

    assert_prolog_success!(&mut wam, "?- a(X).", [["X = c"]]);
}

#[test]
fn test_queries_on_lists()
{
    let mut wam = Machine::new();

    submit(&mut wam, "p([Z, W]).");

    assert_prolog_success!(&mut wam, "?- p([Z, Z]).", [["Z = _0"]]);
    assert_prolog_failure!(&mut wam, "?- p([Z, W, Y]).");
    assert_prolog_success!(&mut wam, "?- p([Z | W]).", [["Z = _0", "W = [_3]"]]);
    assert_prolog_success!(&mut wam, "?- p([Z | [Z]]).", [["Z = _0"]]);
    assert_prolog_success!(&mut wam, "?- p([Z | [W]]).", [["Z = _2", "W = _0"]]);
    assert_prolog_failure!(&mut wam, "?- p([Z | []]).");

    submit(&mut wam, "p([Z, Z]).");

    assert_prolog_success!(&mut wam, "?- p([Z, Z]).", [["Z = _0"]]);
    assert_prolog_failure!(&mut wam, "?- p([Z, W, Y]).");
    assert_prolog_success!(&mut wam, "?- p([Z | W]).", [["Z = _0", "W = [_0]"]]);
    assert_prolog_success!(&mut wam, "?- p([Z | [Z]]).", [["Z = _0"]]);
    assert_prolog_success!(&mut wam, "?- p([Z | [W]]).", [["Z = _0", "W = _0"]]);
    assert_prolog_failure!(&mut wam, "?- p([Z | []]).");

    submit(&mut wam, "p([Z]).");

    assert_prolog_failure!(&mut wam, "?- p([Z, Z]).");
    assert_prolog_failure!(&mut wam, "?- p([Z, W, Y]).");
    assert_prolog_success!(&mut wam, "?- p([Z | W]).", [["W = []", "Z = _0"]]);
    assert_prolog_failure!(&mut wam, "?- p([Z | [Z]]).");
    assert_prolog_failure!(&mut wam, "?- p([Z | [W]]).");
    assert_prolog_success!(&mut wam, "?- p([Z | []]).", [["Z = _0"]]);

    submit(&mut wam, "member(X, [X|_]).
                      member(X, [_|Xs]) :- member(X, Xs).");

    assert_prolog_failure!(&mut wam, "?- member(a, [c, [X, Y]]).");
    assert_prolog_failure!(&mut wam, "?- member(c, [a, [X, Y]]).");
    assert_prolog_success!(&mut wam, "?- member(a, [a, [X, Y]]).", [["X = _2", "Y = _0"]]);

    assert_prolog_success!(&mut wam, "?- member(a, [X, Y, Z]).", [["Y = _2", "X = a",  "Z = _0"],
                                                                  ["Y = a",  "X = _4", "Z = _0"],
                                                                  ["Y = _2",  "X = _4", "Z = a"]]);

    assert_prolog_success!(&mut wam, "?- member([X, X], [a, [X, Y]]).", [["X = _0", "Y = _0"]]);
    assert_prolog_success!(&mut wam, "?- member([X, X], [a, [b, c], [b, b], [Z, x], [d, f]]).",
                           [["Z = _14", "X = b"],
                            ["Z = x",   "X = x"]]);
    assert_prolog_failure!(&mut wam, "?- member([X, X], [a, [b, c], [b, d], [foo, x], [d, f]]).");
    assert_prolog_success!(&mut wam, "?- member([X, Y], [a, [b, c], [b, b], [Z, x], [d, f]]).",
                           [["X = b", "Y = c", "Z = _14"],
                            ["X = b", "Y = b", "Z = _14"],
                            ["X = _2", "Y = x", "Z = _2"],
                            ["X = d", "Y = f", "Z = _14"]]);
    assert_prolog_failure!(&mut wam, "?- member([X, Y, Y], [a, [b, c], [b, b], [Z, x], [d, f]]).");
    assert_prolog_failure!(&mut wam, "?- member([X, Y, Z], [a, [b, c], [b, b], [Z, x], [d, f]]).");
}

#[test]
fn test_queries_on_conjuctive_queries() {
    let mut wam = Machine::new();

    submit(&mut wam, "p(a, b).");
    submit(&mut wam, "q(b, c).");

    assert_prolog_success!(&mut wam, "?- p(X, Y), q(Y, Z).", [["X = a", "Z = c", "Y = b"]]);
    assert_prolog_failure!(&mut wam, "?- p(X, Y), q(Y, X).");

    submit(&mut wam, "p(a, [f(g(X))]).");
    submit(&mut wam, "q(Y, c).");

    assert_prolog_success!(&mut wam, "?- p(X, Y), q(Y, Z).", [["Y = [f(g(_9))]", "X = a", "Z = c"]]);
    assert_prolog_failure!(&mut wam, "?- p(X, Y), q(Y, X).");

    submit(&mut wam, "member(X, [X|_]).
                      member(X, [_|Xs]) :- member(X, Xs).");

    assert_prolog_success!(&mut wam, "?- member(X, [a,b,c]), member(X, [a,b,c]).",
                           [["X = a"],
                            ["X = b"],
                            ["X = c"]]);
    assert_prolog_success!(&mut wam, "?- member(X, [a,b,c]), member(X, [b,c]).",
                           [["X = b"],
                            ["X = c"]]);
    assert_prolog_success!(&mut wam, "?- member(X, [a,c]), member(X, [b,c]).",
                           [["X = c"]]);
    assert_prolog_success!(&mut wam, "?- member(X, [a,b,c,d]), !, member(X, [a,d]).",
                           [["X = a"]]);
    assert_prolog_failure!(&mut wam, "?- member(X, [a,b,c,d]), !, member(X, [e]).");
    assert_prolog_success!(&mut wam, "?- member([X,X],[a,b,c,[d,d],[e,d]]),
                                         member(X, [a,b,c,d,e,f,g]),
                                         member(Y, [X, a, b, c, d]).",
                           [["X = d", "Y = d"],
                            ["X = d", "Y = a"],
                            ["X = d", "Y = b"],
                            ["X = d", "Y = c"],
                            ["X = d", "Y = d"]]);

    submit(&mut wam, "p(a, [f(g(X))]). p(X, c) :- c.");
    submit(&mut wam, "c.");
    submit(&mut wam, "q(Y, c).");

    assert_prolog_success!(&mut wam, "?- p(X, Y), q(Y, Z).",
                           [["X = a",  "Z = c", "Y = [f(g(_9))]"],
                            ["X = _0", "Z = c", "Y = c"]]);
    assert_prolog_success!(&mut wam, "?- p(X, Y), !, q(Y, Z).",
                           [["Z = c", "Y = [f(g(_9))]", "X = a"]]);

    submit(&mut wam, "q([f(g(x))], Z). q([f(g(y))], Y). q([f(g(z))], a).");

    assert_prolog_success!(&mut wam, "?- p(X, Y), q(Y, Z).",
                           [["Z = _11", "X = a", "Y = [f(g(x))]"],
                            ["Z = _11", "X = a", "Y = [f(g(y))]"],
                            ["Z = a", "X = a", "Y = [f(g(z))]"]]);
    assert_prolog_success!(&mut wam, "?- p(X, Y), !, q(Y, Z).",
                           [["X = a", "Y = [f(g(x))]", "Z = _11"],
                            ["X = a", "Y = [f(g(y))]", "Z = _11"],
                            ["X = a", "Y = [f(g(z))]", "Z = a"]]);
    assert_prolog_success!(&mut wam, "?- p(X, Y), !, q(Y, X).",
                           [["X = a", "Y = [f(g(x))]"],
                            ["X = a", "Y = [f(g(y))]"],
                            ["X = a", "Y = [f(g(z))]"]]);

    submit(&mut wam, "p(X, [f(g(x))]). p(X, [f(g(y))]). p(X, [f(g(z))]).");

    assert_prolog_failure!(&mut wam, "?- q(f(X), Y), p(X, Y).");
    assert_prolog_success!(&mut wam, "?- q(X, Y), p(X, Y).",
                           [["Y = [f(g(x))]", "X = [f(g(x))]"],
                            ["Y = [f(g(y))]", "X = [f(g(x))]"],
                            ["Y = [f(g(z))]", "X = [f(g(x))]"],
                            ["Y = [f(g(x))]", "X = [f(g(y))]"],
                            ["Y = [f(g(y))]", "X = [f(g(y))]"],
                            ["Y = [f(g(z))]", "X = [f(g(y))]"]]);
    assert_prolog_success!(&mut wam, "?- p(X, Y), q(X, Y).",
                           [["Y = [f(g(x))]", "X = [f(g(x))]"],
                            ["Y = [f(g(x))]", "X = [f(g(y))]"],
                            ["Y = [f(g(y))]", "X = [f(g(x))]"],
                            ["Y = [f(g(y))]", "X = [f(g(y))]"],
                            ["Y = [f(g(z))]", "X = [f(g(x))]"],
                            ["Y = [f(g(z))]", "X = [f(g(y))]"]]);
    assert_prolog_success!(&mut wam, "?- p(X, Y), q(Y, X).",
                           [["Y = [f(g(x))]", "X = _10"],
                            ["Y = [f(g(y))]", "X = _10"],
                            ["Y = [f(g(z))]", "X = a"]]);
    assert_prolog_success!(&mut wam, "?- q(X, Y), p(Y, X).",
                           [["Y = _9", "X = [f(g(x))]"],
                            ["Y = _9", "X = [f(g(y))]"],
                            ["Y = a"    , "X = [f(g(z))]"]]);
}

#[test]
fn test_queries_on_call_n()
{
    let mut wam = Machine::new();

    submit(&mut wam, "maplist(_, []).
                      maplist(P, [X|Xs]) :- call(P, X), maplist(P, Xs).");
    submit(&mut wam, "f(a). f(b). f(c).");

    assert_prolog_success!(&mut wam, "?- maplist(f, [X,Y,Z]).",
                           [["X = a", "Y = a", "Z = a"],
                            ["X = a", "Y = a", "Z = b"],
                            ["X = a", "Y = a", "Z = c"],
                            ["X = a", "Y = b", "Z = a"],
                            ["X = a", "Y = b", "Z = b"],
                            ["X = a", "Y = b", "Z = c"],
                            ["X = a", "Y = c", "Z = a"],
                            ["X = a", "Y = c", "Z = b"],
                            ["X = a", "Y = c", "Z = c"],
                            ["X = b", "Y = a", "Z = a"],
                            ["X = b", "Y = a", "Z = b"],
                            ["X = b", "Y = a", "Z = c"],
                            ["X = b", "Y = b", "Z = a"],
                            ["X = b", "Y = b", "Z = b"],
                            ["X = b", "Y = b", "Z = c"],
                            ["X = b", "Y = c", "Z = a"],
                            ["X = b", "Y = c", "Z = b"],
                            ["X = b", "Y = c", "Z = c"],
                            ["X = c", "Y = a", "Z = a"],
                            ["X = c", "Y = a", "Z = b"],
                            ["X = c", "Y = a", "Z = c"],
                            ["X = c", "Y = b", "Z = a"],
                            ["X = c", "Y = b", "Z = b"],
                            ["X = c", "Y = b", "Z = c"],
                            ["X = c", "Y = c", "Z = a"],
                            ["X = c", "Y = c", "Z = b"],
                            ["X = c", "Y = c", "Z = c"]]);

    assert_prolog_success!(&mut wam, "?- maplist(f, [a,Y,Z]).",
                           [["Y = a", "Z = a"],
                            ["Y = a", "Z = b"],
                            ["Y = a", "Z = c"],
                            ["Y = b", "Z = a"],
                            ["Y = b", "Z = b"],
                            ["Y = b", "Z = c"],
                            ["Y = c", "Z = a"],
                            ["Y = c", "Z = b"],
                            ["Y = c", "Z = c"]]);

    assert_prolog_success!(&mut wam, "?- maplist(f, [X,a,b]).",
                           [["X = a"],
                            ["X = b"],
                            ["X = c"]]);
    assert_prolog_success!(&mut wam, "?- maplist(f, [c,a,b]).");
    assert_prolog_failure!(&mut wam, "?- maplist(f, [d,e,f]).");
    assert_prolog_success!(&mut wam, "?- maplist(f, []).");
    assert_prolog_failure!(&mut wam, "?- maplist(f(X), [a,b,c]).");

    submit(&mut wam, "f(X) :- call(X), call(X).");
    submit(&mut wam, "p(x). p(y).");

    assert_prolog_failure!(&mut wam, "?- f(p).");
    assert_prolog_success!(&mut wam, "?- f(p(X)).", [["X = x"],
                                                     ["X = y"]]);
    assert_prolog_success!(&mut wam, "?- f(p(x)).");
    assert_prolog_failure!(&mut wam, "?- f(p(w)).");
    assert_prolog_failure!(&mut wam, "?- f(p(X, Y)).");

    submit(&mut wam, "f(P) :- call(P, X), call(P, Y).");

    assert_prolog_success!(&mut wam, "?- f(p).");
    assert_prolog_failure!(&mut wam, "?- f(non_existent).");

    submit(&mut wam, "f(P, X, Y) :- call(P, X), call(P, Y).");

    assert_prolog_success!(&mut wam, "?- f(p, X, Y).", [["Y = x", "X = x"],
                                                        ["Y = y", "X = x"],
                                                        ["Y = x", "X = y"],
                                                        ["Y = y", "X = y"]]);
    assert_prolog_success!(&mut wam, "?- f(p, x, Y).", [["Y = x"],
                                                        ["Y = y"]]);
    assert_prolog_success!(&mut wam, "?- f(p, X, y).", [["X = x"],
                                                        ["X = y"]]);
    assert_prolog_success!(&mut wam, "?- f(p, x, y).");
    assert_prolog_failure!(&mut wam, "?- f(p, X, z).");
    assert_prolog_failure!(&mut wam, "?- f(p, z, Y).");

    assert_prolog_success!(&mut wam, "?- call(p, X).", [["X = x"],
                                                        ["X = y"]]);
    assert_prolog_success!(&mut wam, "?- call(p, x).");
    assert_prolog_success!(&mut wam, "?- call(p, y).");
    assert_prolog_failure!(&mut wam, "?- call(p, z).");

    submit(&mut wam, "r(f(X)) :- p(X). r(g(Y)) :- p(Y).");

    assert_prolog_success!(&mut wam, "?- f(r, X, Y).",
                           [["X = f(x)", "Y = f(x)"],
                            ["X = f(x)", "Y = f(y)"],
                            ["X = f(x)", "Y = g(x)"],
                            ["X = f(x)", "Y = g(y)"],
                            ["X = f(y)", "Y = f(x)"],
                            ["X = f(y)", "Y = f(y)"],
                            ["X = f(y)", "Y = g(x)"],
                            ["X = f(y)", "Y = g(y)"],
                            ["X = g(x)", "Y = f(x)"],
                            ["X = g(x)", "Y = f(y)"],
                            ["X = g(x)", "Y = g(x)"],
                            ["X = g(x)", "Y = g(y)"],
                            ["X = g(y)", "Y = f(x)"],
                            ["X = g(y)", "Y = f(y)"],
                            ["X = g(y)", "Y = g(x)"],
                            ["X = g(y)", "Y = g(y)"]]);
    assert_prolog_success!(&mut wam, "?- f(r, X, X).",
                           [["X = f(x)"],
                            ["X = f(y)"],
                            ["X = g(x)"],
                            ["X = g(y)"]]);
    assert_prolog_success!(&mut wam, "?- f(r, f(X), g(Y)).",
                           [["X = x", "Y = x"],
                            ["X = x", "Y = y"],
                            ["X = y", "Y = x"],
                            ["X = y", "Y = y"]]);
    assert_prolog_failure!(&mut wam, "?- f(r, j(X), h(Y)).");

    submit(&mut wam, "p(one, one). p(one, two). p(two, two).");

    assert_prolog_success!(&mut wam, "?- f(p(one), X, Y).",
                           [["X = one", "Y = one"],
                            ["X = one", "Y = two"],
                            ["X = two", "Y = one"],
                            ["X = two", "Y = two"]]);
    assert_prolog_success!(&mut wam, "?- f(p(one), X, X).",
                           [["X = one"],
                            ["X = two"]]);
    assert_prolog_success!(&mut wam, "?- f(p(one), one, Y).",
                           [["Y = one"],
                            ["Y = two"]]);
    assert_prolog_success!(&mut wam, "?- f(p(one), one, two).");
    assert_prolog_failure!(&mut wam, "?- f(p(one), one, three).");

    assert_prolog_failure!(&mut wam, "?- f(p(two), one, two).");
    assert_prolog_failure!(&mut wam, "?- f(p(two), two, one).");
    assert_prolog_success!(&mut wam, "?- f(p(two), two, two).");
    assert_prolog_failure!(&mut wam, "?- f(p(two), two, three).");

    assert_prolog_failure!(&mut wam, "?- f(p(three), X, Y).");
    assert_prolog_failure!(&mut wam, "?- f(p(three), X, X).");
    assert_prolog_failure!(&mut wam, "?- f(p(three), one, Y).");
    assert_prolog_failure!(&mut wam, "?- f(p(three), one, two).");
    assert_prolog_failure!(&mut wam, "?- f(p(three), one, three).");

    submit(&mut wam, "f(P, X) :- call(P, X).");

    assert_prolog_success!(&mut wam, "?- f(p(one), one).");
    assert_prolog_success!(&mut wam, "?- f(p(two), two).");
    assert_prolog_failure!(&mut wam, "?- f(p(two), one).");
    assert_prolog_failure!(&mut wam, "?- f(p(three), one).");
    assert_prolog_failure!(&mut wam, "?- f(p(one), three).");
    assert_prolog_failure!(&mut wam, "?- f(p(two), three).");

    submit(&mut wam, "p(f(g(X)), compound, [lists,are,good]).");

    assert_prolog_success!(&mut wam, "?- call(p(f(g(X))), Y, Z).",
                           [["Y = compound", "Z = [lists, are, good]", "X = _3"]]);

    submit(&mut wam, "david_lynch(coffee).
                      david_lynch(pie).
                      david_lynch(kyle(Film)) :- kyle(Film).");

    submit(&mut wam, "kyle(dune).
                      kyle(blue_velvet).
                      kyle(showgirls).
                      kyle(flintstones).");

    assert_prolog_success!(&mut wam, "?- call(david_lynch, X).",
                           [["X = coffee"],
                            ["X = pie"],
                            ["X = kyle(dune)"],
                            ["X = kyle(blue_velvet)"],
                            ["X = kyle(showgirls)"],
                            ["X = kyle(flintstones)"]]);
    assert_prolog_success!(&mut wam, "?- call(david_lynch, kyle(Film)).",
                           [["Film = dune"],
                            ["Film = blue_velvet"],
                            ["Film = showgirls"],
                            ["Film = flintstones"]]);
    assert_prolog_failure!(&mut wam, "?- call(david_lynch, kyle(Film), _).");

    submit(&mut wam, "call_mult(P, X) :- call(call(P), X).");

    assert_prolog_success!(&mut wam, "?- call_mult(p(X), Y).",
                           [["Y = one", "X = one"],
                            ["Y = two", "X = one"],
                            ["Y = two", "X = two"]]);
    assert_prolog_success!(&mut wam, "?- call_mult(p(X), X).",
                           [["X = one"],
                            ["X = two"]]);
    assert_prolog_success!(&mut wam, "?- call_mult(p(one), X).",
                           [["X = one"],
                            ["X = two"]]);
    assert_prolog_success!(&mut wam, "?- call_mult(p(X), one).",
                           [["X = one"]]);

    assert_prolog_failure!(&mut wam, "?- call_mult(p(two), one).");
    assert_prolog_success!(&mut wam, "?- call_mult(p(two), two).");

    assert_prolog_success!(&mut wam, "?- call(call(p(one)), X), call(call(p(two)), two).",
                           [["X = one"],
                            ["X = two"]]);
    assert_prolog_success!(&mut wam, "?- call(call(p(one, X))), call(call(p(two, two))).",
                           [["X = one"],
                            ["X = two"]]);
    assert_prolog_failure!(&mut wam, "?- call(call(p(one)), X), call(call(p(two)), one).");
    assert_prolog_success!(&mut wam, "?- call(call(p(X)), X), call(call(p(Y)), Y).",
                           [["X = one", "Y = one"],
                            ["X = one", "Y = two"],
                            ["X = two", "Y = one"],
                            ["X = two", "Y = two"]]);
    assert_prolog_success!(&mut wam, "?- call(call(p(X)), Y), call(call(p(Y)), X).",
                           [["X = one", "Y = one"],
                            ["X = two", "Y = two"]]);
    assert_prolog_success!(&mut wam, "?- call(call(p), X, Y), call(call(call(p)), X, Y).",
                           [["X = one", "Y = one"],
                            ["Y = two", "X = one"],
                            ["Y = two", "X = two"]]);
    assert_prolog_success!(&mut wam, "?- call(call(p), X, Y), call(call(call(p(X))), Y).",
                           [["X = one", "Y = one"],
                            ["Y = two", "X = one"],
                            ["Y = two", "X = two"]]);
    assert_prolog_failure!(&mut wam, "?- call(call(p), X, Y), call(call(call(p(X))), X, Y).");
    assert_prolog_success!(&mut wam, "?- call(call(p), X, Y), call(call(call(p(X))), X).",
                           [["X = one", "Y = one"],
                            ["Y = two", "X = one"],
                            ["Y = two", "X = two"]]);

    submit(&mut wam, "f(call(f, undefined)). f(undefined).");
    submit(&mut wam, "call_var(P) :- P.");

    assert_prolog_success!(&mut wam, "?- f(X), call_var(X).",
                           [["X = call(f, undefined)"]]);
    assert_prolog_success!(&mut wam, "?- f(call(f, Q)), call_var(call(f, Q)).",
                           [["Q = undefined"]]);
    assert_prolog_failure!(&mut wam, "?- call_var(call(undefined, Q)).");

    assert_prolog_failure!(&mut wam, "?- call(call).");
    assert_prolog_failure!(&mut wam, "?- call(call(call)).");
    assert_prolog_failure!(&mut wam, "?- call(call(call(call))).");
    assert_prolog_failure!(&mut wam, "?- call(call(call(call(call)))).");
    assert_prolog_failure!(&mut wam, "?- call(call(call(call(call(call))))).");
    assert_prolog_success!(&mut wam, "?- call(call(call(call(call(call(p(X))))))).",
                           [["X = x"],
                            ["X = y"]]);
}

#[test]
fn test_queries_on_arithmetic()
{
    let mut wam = Machine::new();

    assert_prolog_success!(&mut wam, "?- X is 1, X is X.", [["X = 1"]]);
    assert_prolog_failure!(&mut wam, "?- X is 1, X is X + 1.");
    assert_prolog_success!(&mut wam, "?- X is 1, X is X + 0.", [["X = 1"]]);
    assert_prolog_success!(&mut wam, "?- X is 1, X is X * 1.", [["X = 1"]]);
    assert_prolog_failure!(&mut wam, "?- X is 1, X is X * 2.");

    // assert_prolog_failure!(&mut wam, "?- X is 1 + a.");
    // assert_prolog_failure!(&mut wam, "?- X is 1 + Y.");
    assert_prolog_success!(&mut wam, "?- Y is 2 + 2 - 2, X is 1 + Y, X = 3.",
                           [["X = 3", "Y = 2"]]);
    assert_prolog_failure!(&mut wam, "?- Y is 2 + 2 - 2, X is 1 + Y, X = 2.");

    assert_prolog_success!(&mut wam, "?- 6 is 6.");
    assert_prolog_success!(&mut wam, "?- 6 is 3 + 3.");
    assert_prolog_success!(&mut wam, "?- 6 is 3 * 2.");
    assert_prolog_failure!(&mut wam, "?- 7 is 3 * 2.");
    assert_prolog_failure!(&mut wam, "?- 7 is 3.5 * 2.");
    assert_prolog_success!(&mut wam, "?- 7.0 is 3.5 * 2.");
    assert_prolog_success!(&mut wam, "?- 7.0 is 14 / 2.");
    assert_prolog_failure!(&mut wam, "?- 4.666 is 14.0 / 3.");
    assert_prolog_success!(&mut wam, "?- 4.0 is 8.0 / 2.");

    submit(&mut wam, "f(X) :- X is 5 // 0.");

    assert_prolog_success!(&mut wam, "?- catch(f(X), error(evaluation_error(E), _), true), E = zero_divisor.",
                           [["E = zero_divisor", "X = _1"]]);

    submit(&mut wam, "f(X) :- X is (5 rdiv 1) / 0.");

    assert_prolog_success!(&mut wam, "?- catch(f(X), error(evaluation_error(E), _), true), E = zero_divisor.",
                           [["E = zero_divisor", "X = _1"]]);

    submit(&mut wam, "f(X) :- X is 5.0 / 0.");

    assert_prolog_success!(&mut wam, "?- catch(f(X), error(evaluation_error(E), _), true), E = zero_divisor.",
                           [["E = zero_divisor", "X = _1"]]);

    assert_prolog_success!(&mut wam, "?- X is ((3 + 4) // 2) + 2 - 1 // 1, Y is 2+2, Z is X+Y.",
                           [["Y = 4", "X = 4", "Z = 8"]]);

    assert_prolog_success!(&mut wam, "?- X is ((3 + 4) // 2) + 2 - 1 // 1, Y is 2+2, Z = 8, Y is 4.",
                           [["Y = 4", "X = 4", "Z = 8"]]);

    assert_prolog_success!(&mut wam, "?- X is (3 rdiv 4) / 2, Y is 3 rdiv 8, X = Y.",
                           [["X = 3/8", "Y = 3/8"]]);

    assert_prolog_success!(&mut wam, "?- X is 10 xor -4, X is -10.", [["X = -10"]]);
    assert_prolog_success!(&mut wam, "?- X is 4 xor -7, X is -3.", [["X = -3"]]);
    assert_prolog_success!(&mut wam, "?- X is 10 xor 5 + 55, X = 70.", [["X = 70"]]);

    assert_prolog_success!(&mut wam, "?- X is 10 rem -3, X = 1.",   [["X = 1"]]);
    assert_prolog_success!(&mut wam, "?- X is 10 mod -3, X is -2.", [["X = -2"]]);

    assert_prolog_success!(&mut wam, "?- call(is, X, 3 + 4).", [["X = 7"]]);

    assert_prolog_success!(&mut wam, "?- Y is 3 + 3, call(is, X, Y + 4).", [["Y = 6", "X = 10"]]);
    assert_prolog_success!(&mut wam, "?- call(is, X, 3 + 4.5).", [["X = 7.5"]]);
    assert_prolog_success!(&mut wam, "?- X is 2 rdiv 3, call(is, Y, X*X).", [["X = 2/3", "Y = 4/9"]]);

    assert_prolog_failure!(&mut wam, "?- call(>, 3, 3 + 3).");
    assert_prolog_failure!(&mut wam, "?- X is 3 + 3, call(>, 3, X).");

    assert_prolog_success!(&mut wam, "?- X is 3 + 3, call(<, 3, X).", [["X = 6"]]);
    assert_prolog_success!(&mut wam, "?- X is 3 + 3, X =:= 3 + 3.", [["X = 6"]]);

    assert_prolog_success!(&mut wam, "?- catch(call(is, X, 3 // 0), error(E, _), true).",
                           [["X = _5", "E = evaluation_error(zero_divisor)"]]);

    assert_prolog_success!(&mut wam, "?- catch(call(is, X, 3 // 3), _, true).", [["X = 1"]]);

    submit(&mut wam, "f(X, Sum) :- ( integer(X) -> Sum is X + X * X + 3 ;
                                     var(X) -> Sum = 1, X = 1 ).");

    assert_prolog_success!(&mut wam, "?- f(X, Sum).", [["X = 1", "Sum = 1"]]);
    assert_prolog_success!(&mut wam, "?- f(5, Sum).", [["Sum = 33"]]);
    assert_prolog_success!(&mut wam, "?- f(5, 33).");
    assert_prolog_failure!(&mut wam, "?- f(5, 32).");

    // exponentiation.

    // the ~ operators tests whether |X - Y| <= 1/10000...
    // or whatever degree of approximation used by Newton's method in rational_pow.
    submit(&mut wam, ":- op(900, xfx, ~).");
    submit(&mut wam, "X ~ Y :- abs(X - Y) =< 1 rdiv 10000.");

    assert_prolog_success!(&mut wam, "?- X is 3 ** 3.",
                           [["X = 27"]]);
    assert_prolog_success!(&mut wam, "?- X is 3 ** 0.",
                           [["X = 1"]]);
    assert_prolog_success!(&mut wam, "?- X is 3 ** -0.",
                           [["X = 1"]]);
    assert_prolog_success!(&mut wam, "?- X is 3 ** 1.",
                           [["X = 3"]]);
    assert_prolog_success!(&mut wam, "?- X is 3 ** -3.",
                           [["X = 1/27"]]);
    assert_prolog_success!(&mut wam, "?- X is (-3) ** 3.",
                           [["X = -27"]]);
    assert_prolog_success!(&mut wam, "?- X is (-3) ** 3.",
                           [["X = -27"]]);
    assert_prolog_success!(&mut wam, "?- X is (-3) ** 0.",
                           [["X = 1"]]);
    assert_prolog_success!(&mut wam, "?- X is (-3) ** -0.",
                           [["X = 1"]]);
    assert_prolog_success!(&mut wam, "?- X is (-3) ** 1.",
                           [["X = -3"]]);
    assert_prolog_success!(&mut wam, "?- X is (-3) ** -3.",
                           [["X = -1/27"]]);
    assert_prolog_success!(&mut wam, "?- X is (1 rdiv 27) ** -3, X ~ 19683.");
    assert_prolog_success!(&mut wam, "?- X is (-1 rdiv 27) ** -3, X ~ -19683.");

    assert_prolog_success!(&mut wam, "?- X is 0.0 ** 0.",
                           [["X = 1.0"]]);
    assert_prolog_success!(&mut wam, "?- catch(_ is 0.0 ** -2342, error(E, _), true).",
                           [["E = evaluation_error(no_roots)"]]);
    assert_prolog_success!(&mut wam, "?- X is 0.0 ** 2342.",
                           [["X = 0"]]);

    assert_prolog_success!(&mut wam, "?- catch(_ is (-3) ** (1 rdiv 2), error(E, _), true).",
                           [["E = evaluation_error(no_roots)"]]);
    assert_prolog_success!(&mut wam, "?- catch(_ is (-3/2) ** (1 rdiv 2), error(E, _), true).",
                           [["E = evaluation_error(no_roots)"]]);
    assert_prolog_success!(&mut wam, "?- catch(_ is (-3 rdiv 2) ** (1 rdiv 4), error(E, _), true).",
                           [["E = evaluation_error(no_roots)"]]);
    assert_prolog_success!(&mut wam, "?- catch(_ is (-3 rdiv 2) ** (-1 rdiv 4), error(E, _), true).",
                           [["E = evaluation_error(no_roots)"]]);
    assert_prolog_success!(&mut wam, "?- catch(_ is 0 ** (-5 rdiv 4), error(E, _), true).",
                           [["E = evaluation_error(no_roots)"]]);

    assert_prolog_success!(&mut wam, "?- X is 3 ** (1 rdiv 3), Y is X ** 3, Y ~ 3.");
    assert_prolog_success!(&mut wam, "?- X is (-3) ** (1 rdiv 3), Y is X ** 3, Y ~ -3.");
    assert_prolog_failure!(&mut wam, "?- X is (-5) ** (1 rdiv 3), Y is X ** 3, Y ~ -3.");
    assert_prolog_failure!(&mut wam, "?- X is 5 ** (1 rdiv 3), Y is X ** 3, Y ~ 3.");
    assert_prolog_failure!(&mut wam, "?- X is (1 rdiv 3) ** 0.5, Y is X ** 2, X ~ Y.");
    assert_prolog_success!(&mut wam, "?- X is (1 rdiv 3) ** 0.5, Y is X ** 2, 1 rdiv 3 ~ Y.");

    assert_prolog_success!(&mut wam, "?- X is (-5) ** (-1 rdiv 3), Y is X ** 3, Y ~ -1 rdiv 5.");
    assert_prolog_failure!(&mut wam, "?- X is (-5) ** (-1 rdiv 3), Y is X ** 3, Y ~ 1 rdiv 5.");

    assert_prolog_success!(&mut wam, "?- X is (0 rdiv 5) ** 5.",
                           [["X = 0"]]);
    assert_prolog_success!(&mut wam, "?- X is (-0 rdiv 5) ** 5.",
                           [["X = 0"]]);
    assert_prolog_success!(&mut wam, "?- X is (0 rdiv 5) ** 0.",
                           [["X = 1.0"]]);
    assert_prolog_success!(&mut wam, "?- catch(_ is (0 rdiv 0) ** 5, error(E, _), true).",
                           [["E = evaluation_error(zero_divisor)"]]);
}

#[test]
fn test_queries_on_exceptions()
{
    let mut wam = Machine::new();

    submit(&mut wam, "f(a). f(_) :- throw(stuff).");
    submit(&mut wam, "handle(stuff).");

    assert_prolog_success!(&mut wam, "?- catch(f(X), E, handle(E)).",
                           [["E = _2", "X = a"],
                            ["E = stuff", "X = _1"]]);

    submit(&mut wam, "f(a). f(X) :- g(X).");
    submit(&mut wam, "g(x). g(y). g(z).");
    submit(&mut wam, "handle(x). handle(y).");

    assert_prolog_success!(&mut wam, "?- catch(f(X), X, handle(X)).",
                           [["X = a"],
                            ["X = x"],
                            ["X = y"],
                            ["X = z"]]);
    assert_prolog_success!(&mut wam, "?- catch(f(a), _, handle(X)).",
                           [["X = _4"]]);
    assert_prolog_failure!(&mut wam, "?- catch(f(b), _, handle(X)).");

    submit(&mut wam, "g(x). g(X) :- throw(x).");

    assert_prolog_success!(&mut wam, "?- catch(f(X), x, handle(X)).",
                           [["X = a"],
                            ["X = x"],
                            ["X = x"],
                            ["X = y"]]);
    assert_prolog_success!(&mut wam, "?- catch(f(X), x, handle(z)).",
                           [["X = a"],
                            ["X = x"]]);
    assert_prolog_success!(&mut wam, "?- catch(f(z), x, handle(x)).");
    assert_prolog_success!(&mut wam, "?- catch(f(z), x, handle(y)).");
    assert_prolog_failure!(&mut wam, "?- catch(f(z), x, handle(z)).");

    submit(&mut wam, "f(X) :- throw(stuff).");
    submit(&mut wam, "handle(stuff). handle(other_stuff).");

    // the first 3 cases should deterministically succeed.
    assert_prolog_success!(&mut wam, "?- catch(f(X), E, handle(E)).",
                           [["X = _1", "E = stuff"]]);
    assert_prolog_success!(&mut wam, "?- catch(f(X), E, handle(stuff)).",
                           [["X = _1", "E = stuff"]]);
    assert_prolog_success!(&mut wam, "?- catch(f(X), E, handle(other_stuff)).",
                           [["X = _1", "E = stuff"]]);
    assert_prolog_failure!(&mut wam, "?- catch(f(X), E, handle(not_stuff)).");

    submit(&mut wam, "f(success). f(X) :- catch(g(X), E, handle(E)).");
    submit(&mut wam, "g(g_success). g(g_success_2). g(X) :- throw(X).");
    submit(&mut wam, "handle(x). handle(y). handle(z).");

    assert_prolog_success!(&mut wam, "?- catch(f(X), E, E).",
                           [["X = success", "E = _2"],
                            ["X = g_success", "E = _2"],
                            ["X = g_success_2", "E = _2"],
                            ["X = _1", "E = _2"],
                            ["X = _1", "E = _2"],
                            ["X = _1", "E = _2"]]);
    assert_prolog_failure!(&mut wam, "?- catch(f(fail), _, _).");
    assert_prolog_success!(&mut wam, "?- catch(f(x), _, _).");
    assert_prolog_success!(&mut wam, "?- catch(f(y), _, _).");
    assert_prolog_success!(&mut wam, "?- catch(f(z), _, _).");

    submit(&mut wam, "f(success). f(E) :- catch(g(E), E, handle(E)).");
    submit(&mut wam, "g(g_success). g(g_success_2). g(X) :- throw(X).");
    submit(&mut wam, "handle(x). handle(y). handle(z). handle(v) :- throw(X).");

    assert_prolog_success!(&mut wam, "?- catch(f(X), E, E).",
                           [["X = success", "E = _2"],
                            ["X = g_success", "E = _2"],
                            ["X = g_success_2", "E = _2"],
                            ["X = x", "E = _2"],
                            ["X = y", "E = _2"],
                            ["X = z", "E = _2"]]);

    submit(&mut wam, "handle(x). handle(y). handle(z). handle(v) :- throw(handle_top(X)).");
    submit(&mut wam, "handle_top(an_error_1). handle_top(an_error_2).");

    assert_prolog_success!(&mut wam, "?- catch(f(X), E, E).",
                           [["X = success", "E = _2"],
                            ["X = g_success", "E = _2"],
                            ["X = g_success_2", "E = _2"],
                            ["X = x", "E = _2"],
                            ["X = y", "E = _2"],
                            ["X = z", "E = _2"],
                            ["X = _1", "E = handle_top(an_error_1)"],
                            ["X = _1", "E = handle_top(an_error_2)"]]);

    submit(&mut wam, "handle(x). handle(y). handle(z). handle(v) :- throw(X).");

    assert_prolog_success!(&mut wam, "?- catch(f(X), E, handle_top(E)).",
                           [["X = success", "E = _2"],
                            ["X = g_success", "E = _2"],
                            ["X = g_success_2", "E = _2"],
                            ["X = x", "E = _2"],
                            ["X = y", "E = _2"],
                            ["X = z", "E = _2"],
                            ["E = an_error_1", "X = _1"],
                            ["E = an_error_2", "X = _1"]]);
}

#[test]
fn test_queries_on_skip_max_list() {
    let mut wam = Machine::new();

    // test on proper and empty lists.
    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(N, 5, [], Xs).",
                           [["Xs = []", "N = 0"]]);
    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(N, 5, [a,b,c], Xs).",
                           [["Xs = []", "N = 3"]]);
    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(N, 2, [a,b,c], Xs).",
                           [["Xs = [c]", "N = 2"]]);
    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(N, 3, [a,b,c], Xs).",
                           [["Xs = []", "N = 3"]]);

    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(N, 0, [], Xs).",
                           [["Xs = []", "N = 0"]]);
    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(N, 0, [a,b,c], Xs).",
                           [["Xs = [a, b, c]", "N = 0"]]);
    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(N, 0, [a,b,c], Xs).",
                           [["Xs = [a, b, c]", "N = 0"]]);
    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(N, 0, [a,b,c], Xs).",
                           [["Xs = [a, b, c]", "N = 0"]]);

    assert_prolog_failure!(&mut wam, "?- '$skip_max_list'(4, 0, [], Xs).");
    assert_prolog_failure!(&mut wam, "?- '$skip_max_list'(3, 0, [a,b,c], Xs).");
    assert_prolog_failure!(&mut wam, "?- '$skip_max_list'(2, 0, [a,b,c], Xs).");
    assert_prolog_failure!(&mut wam, "?- '$skip_max_list'(1, 0, [a,b,c], Xs).");

    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(0, 5, [], Xs).",
                           [["Xs = []"]]);
    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(3, 5, [a,b,c], Xs).",
                           [["Xs = []"]]);
    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(2, 2, [a,b,c], Xs).",
                           [["Xs = [c]"]]);
    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(3, 3, [a,b,c], Xs).",
                           [["Xs = []"]]);

    // tests on proper and empty lists with no max.

    // test on proper and empty lists.
    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(N, -1, [], Xs).",
                           [["Xs = []", "N = 0"]]);
    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(N, -1, [a,b,c], Xs).",
                           [["Xs = []", "N = 3"]]);

    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(N, -1, [], Xs).",
                           [["Xs = []", "N = 0"]]);

    assert_prolog_failure!(&mut wam, "?- '$skip_max_list'(4, -1, [], Xs).");
    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(3, -1, [a,b,c], Xs).",
                           [["Xs = []"]]);

    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(0, -1, [], Xs).",
                           [["Xs = []"]]);
    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(3, -1, [a,b,c], Xs).",
                           [["Xs = []"]]);

    // tests on partial lists.
    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(3, 4, [a,b,c|X], Xs0).",
                           [["X = _1", "Xs0 = _1"]]);
    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(3, 3, [a,b,c|X], Xs0).",
                           [["X = _1", "Xs0 = _1"]]);
    assert_prolog_failure!(&mut wam, "?- '$skip_max_list'(3, 2, [a,b,c|X], Xs0).");
    assert_prolog_failure!(&mut wam, "?- '$skip_max_list'(3, 1, [a,b,c|X], Xs0).");
    assert_prolog_failure!(&mut wam, "?- '$skip_max_list'(3, 0, [a,b,c|X], Xs0).");

    // tests on cyclic lists.
    assert_prolog_failure!(&mut wam, "?- Xs = [a,b|Xs], '$skip_max_list'(3, 5, X, Xs0).");
    assert_prolog_failure!(&mut wam, "?- X = [a,b|Y], Y = [c,d|X], '$skip_max_list'(4, 5, X, Xs0).");
    assert_prolog_failure!(&mut wam, "?- X = [a,b|Y], Y = [c,d|X], '$skip_max_list'(4, 3, X, Xs0).");

    // tests on non lists.
    assert_prolog_success!(&mut wam, "?- '$skip_max_list'(N, 9, non_list, Xs).",
                           [["Xs = non_list", "N = 0"]]);
}

#[test]
fn test_queries_on_conditionals()
{
    let mut wam = Machine::new();

    submit(&mut wam, "test(A) :- (   A =:= 2 -> writeq(\"A is 2\")
                                 ;   A =:= 3 -> writeq(\"A is 3\")
                                 ;   A = \"not 2 or 3\"
                                 ).");

    assert_prolog_success!(&mut wam, "?- catch(test(A), error(instantiation_error, _), true).");
    assert_prolog_success!(&mut wam, "?- A = 2, test(A).", [["A = 2"]]);
    assert_prolog_success!(&mut wam, "?- A = 3, test(A), B = 3, test(B).", [["A = 3", "B = 3"]]);

    submit(&mut wam, "f(a). f(b).");
    submit(&mut wam, "g(1). g(2). g(3).");

    submit(&mut wam, "typed_dispatch(X) :- ( var(X) -> f(X)
                                           ; integer(X) -> g(X)
                                           ; atomic(X)).");

    assert_prolog_success!(&mut wam, "?- typed_dispatch(X).", [["X = a"], ["X = b"]]);
    assert_prolog_success!(&mut wam, "?- typed_dispatch(a).");
    assert_prolog_success!(&mut wam, "?- typed_dispatch(b).");
    assert_prolog_success!(&mut wam, "?- typed_dispatch(c).");
    assert_prolog_success!(&mut wam, "?- typed_dispatch(1).");
    assert_prolog_success!(&mut wam, "?- typed_dispatch(2).");
    assert_prolog_success!(&mut wam, "?- typed_dispatch(3).");
    assert_prolog_failure!(&mut wam, "?- typed_dispatch(4).");
    assert_prolog_failure!(&mut wam, "?- typed_dispatch(5).");
    assert_prolog_failure!(&mut wam, "?- typed_dispatch(compound(term)).");

    submit(&mut wam, "f(a). f(b). f(compound(term)).");
    submit(&mut wam, "g(X, Y) :- f(X), (atomic(X) -> X = a ; X = a ; X = compound(Y)).");

    assert_prolog_success!(&mut wam, "?- g(X, Y).",
                           [["Y = _1", "X = a"],
                            ["Y = term", "X = compound(term)"]]);

    assert_prolog_success!(&mut wam, "?- g(X, X).", [["X = a"]]);
    assert_prolog_success!(&mut wam, "?- g(compound(X), X).", [["X = term"]]);
    assert_prolog_success!(&mut wam, "?- g(X, term).", [["X = a"], ["X = compound(term)"]]);
    assert_prolog_success!(&mut wam, "?- g(a, _).");
    assert_prolog_success!(&mut wam, "?- g(X, _), X = a.", [["X = a"]]);

    submit(&mut wam, "g(X) :- var(X) -> (var(X) -> X is 3 + 3 ; X = not_6).");

    assert_prolog_success!(&mut wam, "?- g(X).", [["X = 6"]]);
    assert_prolog_failure!(&mut wam, "?- g(1).");
    assert_prolog_failure!(&mut wam, "?- g(6).");
    assert_prolog_failure!(&mut wam, "?- g(not_6).");

    assert_prolog_success!(&mut wam, "?- f(X), (g(Y), !).", [["X = a", "Y = 6"]]);

    submit(&mut wam, "test(X, [X]) :- (atomic(X) -> true ; throw(type_error(atomic_expected, X))).
                      test(_, _).");

    assert_prolog_success!(&mut wam, "?- catch(test(a, [a]), type_error(E), true).",
                           [["E = _6"], ["E = _6"]]);

    assert_prolog_success!(&mut wam, "?- f(X), call(->, atomic(X), true).",
                           [["X = a"], ["X = b"]]);
}

#[test]
fn test_queries_on_modules()
{
    let mut wam = Machine::new();

    submit(&mut wam, ":- use_module(library(lists)).");

    compile_user_module(&mut wam, "
:- module(my_lists, [local_member/2, reverse/2]).
:- use_module(library(lists), [member/2]).

local_member(X, Xs) :- member(X, Xs).

reverse(Xs, Ys) :- lists:reverse(Xs, Ys).
".as_bytes());

    assert_prolog_success!(&mut wam, "?- my_lists:local_member(1, [1,2,3]).");
    assert_prolog_success!(&mut wam, "?- my_lists:reverse([a,b,c], [c,b,a]).");

    compile_user_module(&mut wam, "
:- module(my_lists_2, [local_member/2]).
:- use_module(library(my_lists), [local_member/2]).
".as_bytes());

    assert_prolog_success!(&mut wam, "?- my_lists_2:local_member(1, [1,2,3]).");
    assert_prolog_success!(&mut wam, "?- catch(local_member(X, Xs), error(E, _), true).",
                           [["X = _1", "E = existence_error(procedure, local_member/2)", "Xs = _2"]]);

    submit(&mut wam, ":- use_module(library(lists), [reverse/2]).");

    assert_prolog_success!(&mut wam, "?- catch(member(_, _), error(existence_error(procedure, P), _), true).",
                           [["P = member/2"]]);
    assert_prolog_success!(&mut wam, "?- reverse(_, _).");

    submit(&mut wam, ":- use_module(library(lists), []).");

    assert_prolog_success!(&mut wam, "?- catch(reverse(_, _), error(existence_error(procedure, P), _), true).",
                           [["P = reverse/2"]]);
}

#[test]
fn test_queries_on_builtins()
{
    let mut wam = Machine::new();

    submit(&mut wam, ":- use_module(library(lists)).");
    submit(&mut wam, ":- use_module(library(control)).");

    assert_prolog_failure!(&mut wam, "?- atom(X).");
    assert_prolog_success!(&mut wam, "?- atom(a).");
    assert_prolog_failure!(&mut wam, "?- atom(\"string\").");
    assert_prolog_success!(&mut wam, "?- atom([]).");
    assert_prolog_failure!(&mut wam, "?- atom(1).");
    assert_prolog_failure!(&mut wam, "?- atom(0).");
    assert_prolog_failure!(&mut wam, "?- atom(0.0).");
    assert_prolog_failure!(&mut wam, "?- atom([a,b,c]).");
    assert_prolog_failure!(&mut wam, "?- atom(atop(the_trees)).");

    assert_prolog_failure!(&mut wam, "?- atomic(X).");
    assert_prolog_success!(&mut wam, "?- atomic(a).");
    assert_prolog_success!(&mut wam, "?- atomic(\"string\").");
    assert_prolog_success!(&mut wam, "?- atomic([]).");
    assert_prolog_success!(&mut wam, "?- atomic(1).");
    assert_prolog_success!(&mut wam, "?- atomic(0).");
    assert_prolog_success!(&mut wam, "?- atomic(0.0).");
    assert_prolog_failure!(&mut wam, "?- atomic([a,b,c]).");
    assert_prolog_failure!(&mut wam, "?- atomic(atop(the_trees)).");

    assert_prolog_success!(&mut wam, "?- var(X), X = 3, atomic(X).", [["X = 3"]]);
    assert_prolog_failure!(&mut wam, "?- var(X), X = 3, var(X).");

    assert_prolog_success!(&mut wam, "?- arg(1, f(a,b,c,d), Arg).", [["Arg = a"]]);
    assert_prolog_success!(&mut wam, "?- arg(2, f(a,b,c,d), Arg).", [["Arg = b"]]);
    assert_prolog_success!(&mut wam, "?- arg(3, f(a,b,c,d), Arg).", [["Arg = c"]]);
    assert_prolog_success!(&mut wam, "?- arg(4, f(a,b,c,d), Arg).", [["Arg = d"]]);

    assert_prolog_success!(&mut wam, "?- catch(arg(N, f, Arg), error(E, _), true).",
                           [["E = instantiation_error", "Arg = _3", "N = _1"]]);

    assert_prolog_failure!(&mut wam, "?- arg(N, f(arg, arg, arg), not_arg).");
    assert_prolog_failure!(&mut wam, "?- arg(1, f(arg, not_arg, not_arg), not_arg).");
    assert_prolog_success!(&mut wam, "?- arg(2, f(arg, not_arg, not_arg), not_arg).");
    assert_prolog_success!(&mut wam, "?- arg(3, f(arg, not_arg, not_arg), not_arg).");

    assert_prolog_success!(&mut wam, "?- functor(f(a,b,c), F, Arity).",
                           [["F = f", "Arity = 3"]]);

    assert_prolog_success!(&mut wam, "?- functor(f(a,b,c), F, N).",
                           [["F = f", "N = 3"]]);
    assert_prolog_failure!(&mut wam, "?- functor(f(a,b,c), g, N).");
    assert_prolog_success!(&mut wam, "?- functor(f(a,b,c), F, 3).", [["F = f"]]);
    assert_prolog_failure!(&mut wam, "?- functor(f(a,b,c), F, 4).");
    assert_prolog_failure!(&mut wam, "?- functor(f(a,b,c), g, 3).");

    assert_prolog_success!(&mut wam, "?- functor(F, f, 0).", [["F = f"]]);

    assert_prolog_success!(&mut wam, "?- functor(Func, f, 3).", [["Func = f(_2, _3, _4)"]]);
    assert_prolog_success!(&mut wam, "?- functor(Func, f, 4).", [["Func = f(_2, _3, _4, _5)"]]);

    assert_prolog_success!(&mut wam, "?- catch(functor(F, \"sdf\", 3), error(E, _), true).",
                           [["E = type_error(atom, [s, d, f])", "F = _1"]]);
    assert_prolog_success!(&mut wam, "?- catch(functor(Func, F, 3), error(E, _), true).",
                           [["E = instantiation_error", "Func = _1", "F = _2"]]);
    assert_prolog_success!(&mut wam, "?- catch(functor(Func, f, N), error(E, _), true).",
                           [["E = instantiation_error", "Func = _1", "N = _3"]]);
    assert_prolog_failure!(&mut wam, "?- catch(functor(Func, f, N), error(E, _), false).");

    assert_prolog_success!(&mut wam, "?- X is 3, call(integer, X).");
    assert_prolog_failure!(&mut wam, "?- X is 3 + 3.5, call(integer, X).");
    assert_prolog_success!(&mut wam, "?- X is 3 + 3.5, \\+ call(integer, X).");
    assert_prolog_success!(&mut wam, "?- X is 3 + 3.5, \\+ integer(X).");

    assert_prolog_success!(&mut wam, "?- Func =.. [atom].", [["Func = atom"]]);
    assert_prolog_success!(&mut wam, "?- Func =.. [\"sdf\"].", [["Func = [s, d, f]"]]);
    assert_prolog_success!(&mut wam, "?- Func =.. [1].", [["Func = 1"]]);
    assert_prolog_success!(&mut wam, "?- catch(Func =.. [1,2], error(type_error(atom, 1), _), true).");
    assert_prolog_success!(&mut wam, "?- f(1,2,3) =.. List.", [["List = [f, 1, 2, 3]"]]);
    assert_prolog_success!(&mut wam, "?- f(1,2,3) =.. [f,1,2,3].");
    assert_prolog_failure!(&mut wam, "?- f(1,2,3) =.. [f,1].");
    assert_prolog_failure!(&mut wam, "?- f(1,2,3) =.. [g,1,2,3].");
    assert_prolog_success!(&mut wam, "?- f(1,2,3) =.. [f,X,Y,Z].",
                           [["X = 1", "Y = 2", "Z = 3"]]);

    assert_prolog_success!(&mut wam, "?- length([a,b,c], N).", [["N = 3"]]);
    assert_prolog_success_with_limit!(&mut wam, "?- length(Xs, N).",
                                      [["N = 0", "Xs = []"],
                                       ["N = 1", "Xs = [_4]"],
                                       ["N = 2", "Xs = [_4, _8]"],
                                       ["N = 3", "Xs = [_4, _8, _12]"],
                                       ["N = 4", "Xs = [_4, _8, _12, _16]"],
                                       ["N = 5", "Xs = [_4, _8, _12, _16, _20]"]],
                                      6);

    assert_prolog_success!(&mut wam, "?- length(Xs, 3).", [["Xs = [_5, _9, _13]"]]);
    assert_prolog_success!(&mut wam, "?- length([], N).", [["N = 0"]]);
    assert_prolog_success!(&mut wam, "?- length(Xs, 0).", [["Xs = []"]]);
    assert_prolog_success!(&mut wam, "?- length([a,b,[a,b,c]], 3).");
    assert_prolog_failure!(&mut wam, "?- length([a,b,[a,b,c]], 2).");
    assert_prolog_success!(&mut wam, "?- catch(length(a, []), error(E, _), true).",
                           [["E = type_error(integer, [])"]]);

    assert_prolog_success!(&mut wam, "?- copy_term([1,2,3], [X,Y,Z]).",
                           [["Z = 3", "Y = 2", "X = 1"]]);
    assert_prolog_success!(&mut wam, "?- copy_term(f(X, [a], Z), f(X, Y, Z)).",
                           [["X = _3", "Y = [a]", "Z = _5"]]);
    assert_prolog_failure!(&mut wam, "?- copy_term(g(X), f(X)).");
    assert_prolog_success!(&mut wam, "?- copy_term(f(X), f(X)).",
                           [["X = _1"]]);
    assert_prolog_success!(&mut wam, "?- copy_term([[[[X, Y], Y], X]], Term).",
                           [["Term = [[[[_22, _26], _26], _22]]", "X = _2", "Y = _0"]]);
    assert_prolog_success!(&mut wam, "?- copy_term([X, [Y, [X]]], Term).",
                           [["Term = [_12, [_16, [_12]]]", "X = _0", "Y = _4"]]);

    // test copy_term on cyclic terms.
    assert_prolog_failure!(&mut wam, "?- X = g(X, Y), Y = f(X), copy_term(Y, g(Z)).");
    assert_prolog_success!(&mut wam, "?- X = g(X, Y), Y = f(X), copy_term(Y, f(Z)).",
                           [["Y = f(g(X, Y))", "X = g(X, f(X))", "Z = g(Z, f(Z))"]]);
    assert_prolog_success!(&mut wam, "?- X = g(X, Y), Y = f(X), copy_term(Y, V).",
                           [["Y = f(g(X, Y))", "X = g(X, f(X))", "V = f(g(_9, V))"]]);
    assert_prolog_success!(&mut wam, "?- f(Y,Y,[X,a,[],Y]) = Term, copy_term(Term, NewTerm).",
                           [["NewTerm = f(_16, _16, [_19, a, [], _16])",
                             "Term = f(_0, Y, [_6, a, [], Y])",
                             "X = _6", "Y = _0"]]);

    assert_prolog_success!(&mut wam, "?- float(3.14159269).");
    assert_prolog_failure!(&mut wam, "?- float(3).");
    assert_prolog_failure!(&mut wam, "?- float(\"sdfsa\").");
    assert_prolog_failure!(&mut wam, "?- float(atom).");
    assert_prolog_failure!(&mut wam, "?- float(structure(functor)).");
    assert_prolog_failure!(&mut wam, "?- float([1,2,3]).");
    assert_prolog_failure!(&mut wam, "?- float([1,2,X]).");
    assert_prolog_failure!(&mut wam, "?- X is 3 rdiv 4, float(X).");

    assert_prolog_success!(&mut wam, "?- X is 3 rdiv 4, rational(X).");
    assert_prolog_failure!(&mut wam, "?- rational(3).");
    assert_prolog_failure!(&mut wam, "?- rational(f(X)).");
    assert_prolog_failure!(&mut wam, "?- rational(\"sdfsa\").");
    assert_prolog_failure!(&mut wam, "?- rational(atom).");
    assert_prolog_failure!(&mut wam, "?- rational(structure(functor)).");
    assert_prolog_failure!(&mut wam, "?- rational([1,2,3]).");
    assert_prolog_failure!(&mut wam, "?- rational([1,2,X]).");

    assert_prolog_success!(&mut wam, "?- compound(functor(compound)).");
    assert_prolog_success!(&mut wam, "?- compound(f(X)).");
    assert_prolog_success!(&mut wam, "?- compound([1,2,3]).");
    assert_prolog_failure!(&mut wam, "?- compound([]).");
    assert_prolog_failure!(&mut wam, "?- compound(3.14159269).");
    assert_prolog_failure!(&mut wam, "?- compound(3).");
    assert_prolog_failure!(&mut wam, "?- compound(\"sdfsa\").");
    assert_prolog_failure!(&mut wam, "?- compound(atom).");

    assert_prolog_failure!(&mut wam, "?- string(functor(string)).");
    assert_prolog_failure!(&mut wam, "?- string(3.14159269).");
    assert_prolog_failure!(&mut wam, "?- string(3).");
    assert_prolog_failure!(&mut wam, "?- string(f(X)).");
    assert_prolog_success!(&mut wam, "?- string(\"sdfsa\").");
    assert_prolog_failure!(&mut wam, "?- string(atom).");
    assert_prolog_failure!(&mut wam, "?- string([1,2,3]).");
    assert_prolog_failure!(&mut wam, "?- string([1,2,X]).");

    assert_prolog_success!(&mut wam, "?- X = nonvar, nonvar(X).");
    assert_prolog_failure!(&mut wam, "?- nonvar(X).");
    assert_prolog_success!(&mut wam, "?- nonvar(f(X)).");
    assert_prolog_success!(&mut wam, "?- nonvar(functor(nonvar)).");
    assert_prolog_success!(&mut wam, "?- nonvar(3.14159269).");
    assert_prolog_success!(&mut wam, "?- nonvar(3).");
    assert_prolog_success!(&mut wam, "?- nonvar(\"sdfsa\").");
    assert_prolog_success!(&mut wam, "?- nonvar(atom).");
    assert_prolog_success!(&mut wam, "?- nonvar([1,2,3]).");
    assert_prolog_success!(&mut wam, "?- nonvar([1,2,X]).");

    assert_prolog_success!(&mut wam, "?- A = f(A), ground(f(f(A))), ground(f(A)), ground(A).");
    assert_prolog_failure!(&mut wam, "?- B = f(A), ground(B).");
    assert_prolog_failure!(&mut wam, "?- B = f(A), ground(A).");

    assert_prolog_success!(&mut wam, "?- ground(x), ground(f(x)), X = f(x), ground(g(f(X), [a,b])).");

    assert_prolog_success!(&mut wam, "?- A = f(A), g(A, B) == g(f(A), B).");
    assert_prolog_failure!(&mut wam, "?- A = f(A), g(A, B) == g(f(A), b).");
    assert_prolog_failure!(&mut wam, "?- A == B.");
    assert_prolog_failure!(&mut wam, "?- A == 12.1.");
    assert_prolog_success!(&mut wam, "?- X = x, f(X, x) == f(x, X).");

    assert_prolog_failure!(&mut wam, "?- A = f(A), g(A, B) \\== g(f(A), B).");
    assert_prolog_success!(&mut wam, "?- A = f(A), g(A, B) \\== g(f(A), b).");
    assert_prolog_success!(&mut wam, "?- A \\== B.");
    assert_prolog_success!(&mut wam, "?- A \\== 12.1.");
    assert_prolog_failure!(&mut wam, "?- X = x, f(X, x) \\== f(x, X).");

    assert_prolog_success!(&mut wam, "?- X @=< Y.");
    assert_prolog_failure!(&mut wam, "?- X @>= Y.");
    assert_prolog_failure!(&mut wam, "?- X @> Y.");
    assert_prolog_success!(&mut wam, "?- X @>= X.");
    assert_prolog_failure!(&mut wam, "?- atom @=< \"string\".");
    assert_prolog_success!(&mut wam, "?- atom @=< atom.");
    assert_prolog_failure!(&mut wam, "?- atom @=< aaa.");
    assert_prolog_success!(&mut wam, "?- atom @>= \"string\".");
    assert_prolog_success!(&mut wam, "?- X is 3 + 3, X @>= Y.");
    assert_prolog_success!(&mut wam, "?- f(X) @>= f(X).");
    assert_prolog_success!(&mut wam, "?- f(X) @>= a.");
    assert_prolog_failure!(&mut wam, "?- f(X) @=< a.");
    assert_prolog_success!(&mut wam, "?- [1,2] @=< [1,2].");
    assert_prolog_failure!(&mut wam, "?- [1,2,3] @=< [1,2].");
    assert_prolog_success!(&mut wam, "?- [] @=< [1,2].");
    assert_prolog_failure!(&mut wam, "?- [] @< 1.");
    assert_prolog_failure!(&mut wam, "?- [] @< \"string\".");
    assert_prolog_failure!(&mut wam, "?- [] @< atom.");
    assert_prolog_success!(&mut wam, "?- atom @< [].");
    assert_prolog_failure!(&mut wam, "?- 1.1 @< 1.");
    assert_prolog_success!(&mut wam, "?- 1.0 @=< 1.");
    assert_prolog_success!(&mut wam, "?- 1 @=< 1.0."); //TODO: currently this succeeds. make it fail.

    assert_prolog_success!(&mut wam, "?- X =@= Y.");
    assert_prolog_failure!(&mut wam, "?- f(X) =@= f(x).");
    assert_prolog_failure!(&mut wam, "?- X \\=@= X.");
    assert_prolog_success!(&mut wam, "?- f(x) =@= f(x).");
    assert_prolog_failure!(&mut wam, "?- [X,Y,Z] =@= [V,W,V].");
    assert_prolog_success!(&mut wam, "?- [X,Y,Z] =@= [V,W,Z].");
    assert_prolog_success!(&mut wam, "?- [X,Y,X] =@= [V,W,V].");
    assert_prolog_success!(&mut wam, "?- g(B) = B, g(A) = A, A =@= B.");

    assert_prolog_success!(&mut wam, "?- keysort([1-1, 1-1], Sorted).",
                           [["Sorted = [1-1, 1-1]"]]);
    assert_prolog_success!(&mut wam, "?- keysort([2-99, 1-a, 3-f(_), 1-z, 1-a, 2-44], Sorted).",
                           [["Sorted = [1-a, 1-z, 1-a, 2-99, 2-44, 3-f(_7)]"]]);
    assert_prolog_success!(&mut wam, "?- keysort([X-1,1-1],[2-1,1-1]).",
                           [["X = 2"]]);

    assert_prolog_failure!(&mut wam, "?- Pairs = [a-a|Pairs], keysort(Pairs, _).");
    assert_prolog_success!(&mut wam, "?- Pairs = [a-a|Pairs], catch(keysort(Pairs, _), error(E, _), true).",
                           [["E = type_error(list, [a-a | _25])", "Pairs = [a-a | Pairs]"]]);

    assert_prolog_success!(&mut wam, "?- keysort([], L).",
                           [["L = []"]]);
    assert_prolog_success!(&mut wam, "?- catch(keysort([a|_], _), error(E, _), true).",
                           [["E = instantiation_error"]]);
    assert_prolog_success!(&mut wam, "?- catch(keysort([],[a|a]),error(Pat, _),true).",
                           [["Pat = type_error(list, [a | a])"]]);
    assert_prolog_success!(&mut wam, "?- catch(keysort(_, _), error(E, _), true).",
                           [["E = type_error(list, _16)"]]);
    assert_prolog_success!(&mut wam, "?- catch(keysort([a-1], [_|b]), error(E, _), true).",
                           [["E = type_error(list, [_27 | b])"]]);
    assert_prolog_success!(&mut wam, "?- catch(keysort([a-1], [a-b,c-d,a]), error(E, _), true).",
                           [["E = type_error(pair, a)"]]);
    assert_prolog_success!(&mut wam, "?- catch(keysort([a], [a-b]), error(E, _), true).",
                           [["E = type_error(pair, a)"]]);

    assert_prolog_success!(&mut wam, "?- catch(sort([a|_], _), error(E, _), true).",
                           [["E = instantiation_error"]]);
    assert_prolog_success!(&mut wam, "?- catch(sort([],[a|a]),error(Pat, _),true).",
                           [["Pat = type_error(list, [a | a])"]]);
    assert_prolog_success!(&mut wam, "?- sort([], L).",
                           [["L = []"]]);
    assert_prolog_success!(&mut wam, "?- catch(sort(_, []), error(E, _), true).",
                           [["E = type_error(list, _16)"]]);
    assert_prolog_success!(&mut wam, "?- catch(sort([a,b,c], not_a_list), error(E, _), true).",
                           [["E = type_error(list, not_a_list)"]]);

    assert_prolog_success!(&mut wam, "?- call(((G = 2 ; fail), B=3, !)).",
                           [["G = 2", "B = 3"]]);

    assert_prolog_success!(&mut wam, "?- call_with_inference_limit((setup_call_cleanup(S=1,(G=2;fail),writeq(S+G>B)), B=3, !), 100, R).",
                           [["G = 2", "B = 3", "R = !", "S = 1"]]);
    assert_prolog_success!(&mut wam, "?- call_with_inference_limit((setup_call_cleanup(S=1,(G=2;fail),writeq(S+G>B)), B=3, !), 10, R).",
                           [["S = _1", "G = _4", "B = _14", "R = inference_limit_exceeded"]]);

    assert_prolog_success!(&mut wam, "?- X = '\\033\\'.",
                           [["X = '\\x1b\\'"]]);
    
    assert_prolog_success!(&mut wam, "?- X = '\\n'.",
                           [["X = '\\n'"]]);
    assert_prolog_success!(&mut wam, "?- X = '\\b'.",
                           [["X = '\\b'"]]);
    assert_prolog_success!(&mut wam, "?- X = '\\v'.",
                           [["X = '\\v'"]]);
    assert_prolog_success!(&mut wam, "?- X = '\\a'.",
                           [["X = '\\a'"]]);
    assert_prolog_success!(&mut wam, "?- X = '\\f'.",
                           [["X = '\\f'"]]);
    assert_prolog_success!(&mut wam, "?- X = '\\b\\r\\f\\t\\n'.",
                           [["X = '\\b\\r\\f\\t\\n'"]]);

    assert_prolog_success!(&mut wam, "?- (- (1)) = -(1).");
    assert_prolog_success!(&mut wam, "?- (- -1) = -(-1).");
    
    assert_prolog_success!(&mut wam, "?- X = ((*)=(*)).",
                           [["X = ((*)=(*))"]]);
    assert_prolog_success!(&mut wam, "?- X = [.,.(.,.,.)].",
                           [["X = ['.', '.'('.', '.', '.')]"]]);
    assert_prolog_success!(&mut wam, "?- X = a+(b*c).",
                           [["X = a+b*c"]]);
    assert_prolog_success!(&mut wam, "?- X = a*(b+c).",
                           [["X = a*(b+c)"]]);
    assert_prolog_success!(&mut wam, "?- X = [:-,-].",
                           [["X = [:-, -]"]]);
    assert_prolog_success!(&mut wam, "?- X = a*(b+c).",
                           [["X = a*(b+c)"]]);
    assert_prolog_success!(&mut wam, "?- X = (-)-(-).",
                           [["X = (-)-(-)"]]);
    assert_prolog_success!(&mut wam, "?- X = ((:-):-(:-)).",
                           [["X = ((:-):-(:-))"]]);
    assert_prolog_success!(&mut wam, "?- X = (a:-b,c).",
                           [["X = (a:-b,c)"]]);
    assert_prolog_success!(&mut wam, "?- X = f((f:-a,b,c)).",
                           [["X = f((f:-a,b,c))"]]);
    assert_prolog_success!(&mut wam, "?- X = f((f:-a,(b,c))).",
                           [["X = f((f:-a,b,c))"]]);
    assert_prolog_success!(&mut wam, "?- X = f((a,b,c)).",
                           [["X = f((a,b,c))"]]);
    assert_prolog_success!(&mut wam, "?- X = f((a,(b,c))).",
                           [["X = f((a,b,c))"]]);
    assert_prolog_success!(&mut wam, "?- X = f(((a,b),c)).",
                           [["X = f(((a,b),c))"]]);
    assert_prolog_success!(&mut wam, "?- X = f(((a,b),(c, d))).",
                           [["X = f(((a,b),c,d))"]]);

    assert_prolog_success!(&mut wam, "?- findall(X, (X = 1 ; X = 2), S).",
                           [["S = [1, 2]", "X = _0"]]);
    assert_prolog_success!(&mut wam, "?- findall(X+Y, (X = 1), S).",
                           [["S = [1+_36]", "X = _1", "Y = _2"]]);
    assert_prolog_success!(&mut wam, "?- findall(X, false, S).",
                           [["S = []", "X = _0"]]);
    assert_prolog_success!(&mut wam, "?- findall(X, (X = 1 ; X = 1), S).",
                           [["S = [1, 1]", "X = _0"]]);
    assert_prolog_failure!(&mut wam, "?- findall(X, (X = 2 ; X = 1), [1, 2]).");
    assert_prolog_success!(&mut wam, "?- findall(X, (X = 1 ; X = 2), [X, Y]).",
                           [["X = 1", "Y = 2"]]);
    assert_prolog_success!(&mut wam, "?- catch(findall(X, 4, S), error(type_error(callable, 4), _), true).",
                           [["S = _3", "X = _1"]]);

    assert_prolog_success!(&mut wam, "?- bagof(X, (X=Y; X=Z), S).",
                           [["S = [_3, _6]", "X = _0", "Y = _3", "Z = _6"]]);
    assert_prolog_success!(&mut wam, "?- bagof(X, (X=1 ; X = 2), X).",
                           [["X = [1, 2]"]]);
    assert_prolog_success!(&mut wam, "?- bagof(X, (X=1 ; X = 2), S).",
                           [["S = [1, 2]", "X = _0"]]);
    assert_prolog_success!(&mut wam, "?- bagof(1, (Y=1 ; Y=2), L).",
                           [["L = [1]", "Y = 1"],
                            ["L = [1]", "Y = 2"]]);

    submit(&mut wam, "b(1, 1). b(1, 1). b(1, 2). b(2, 1). b(2, 2). b(2, 2).");

    assert_prolog_success!(&mut wam, "?- bagof(X, b(X, Y), L).",
                           [["L = [1, Y, 2]", "X = _0", "Y = 1"],
                            ["L = [1, 2, Y]", "X = _0", "Y = 2"]]);

    assert_prolog_success!(&mut wam, "?- bagof(X, (X=Y; X=Z; Y=1), L).",
                           [["L = [_3, _6]", "X = _0", "Y = _3", "Z = _6"],
                            ["L = [_112]", "X = _0", "Y = 1", "Z = _6"]]);

    submit(&mut wam, "a(1, f(_)). a(2, f(_)).");

    assert_prolog_success!(&mut wam, "?- bagof(X, a(X, Y), L).",
                           [["L = [1, 2]", "X = _0", "Y = f(_78)"]]);

    assert_prolog_success!(&mut wam, "?- setof(X, (X = 1 ; X = 2), S).",
                           [["S = [1, 2]", "X = _0"]]);
    assert_prolog_success!(&mut wam, "?- setof(X, (X=Y ; X=Z), S).",
                           [["S = [_3, _6]", "X = _0", "Y = _3", "Z = _6"]]);
    assert_prolog_failure!(&mut wam, "?- setof(X, false, S).");
    assert_prolog_success!(&mut wam, "?- setof(1, (Y=1 ; Y=2), L).",
                           [["L = [1]", "Y = 1"],
                            ["L = [1]", "Y = 2"]]);
    assert_prolog_success!(&mut wam, "?- setof(X, (X=Y; X=Z; Y=1), L).",
                           [["L = [_3, _6]", "X = _0", "Y = _3", "Z = _6"],
                            ["L = [_112]", "Y = 1", "X = _0", "Y = 1", "Z = _6"]]);
    assert_prolog_failure!(&mut wam, "?- setof(X, member(X, [f(U,b),f(V,c)]), [f(a,c),f(a,b)]).");
    assert_prolog_success!(&mut wam, "?- setof(X, member(X, [f(U,b),f(V,c)]), [f(a,b),f(a,c)]).",
                           [["U = a", "V = a", "X = _0"]]);
    assert_prolog_success!(&mut wam, "?- setof(X, member(X, [V,U,f(U),f(V)]), L).",
                           [["L = [_2, _4, f(U), f(V)]", "U = _2", "V = _4", "X = _0"]]);
    assert_prolog_success!(&mut wam, "?- setof(X, member(X, [V,U,f(U),f(V)]), [a,b,f(a),f(b)]).",
                           [["U = a", "V = b", "X = _0"]]);

    assert_prolog_success!(&mut wam, "?- findall(X, (X = 1 ; X = 2), S0, S1).",
                           [["S0 = [1, 2 | _11]", "S1 = _11", "X = _0"]]);
    assert_prolog_success!(&mut wam, "?- findall(X+Y, (X = 1), S0, S1).",
                           [["S0 = [1+_44 | _7]", "S1 = _7", "X = _1", "Y = _2"]]);
    assert_prolog_success!(&mut wam, "?- findall(X, false, S, _).",
                           [["S = []", "X = _0"]]);
    assert_prolog_success!(&mut wam, "?- findall(X, (X = 1 ; X = 1), S0, S1).",
                           [["S0 = [1, 1 | _11]", "S1 = _11", "X = _0"]]);
    assert_prolog_failure!(&mut wam, "?- findall(X, (X = 2 ; X = 1), [1, 2 | S], S).");
    assert_prolog_success!(&mut wam, "?- findall(X, (X = 1 ; X = 2), [X, Y | S], S).",
                           [["S = _11", "X = 1", "Y = 2"]]);
    assert_prolog_success!(&mut wam, "?- catch(findall(X, 4, S0, S1), error(type_error(callable, 4), _), true).",
                           [["S0 = _3", "S1 = _4", "X = _1"]]);

    // bagof & setof with existential variables.
    assert_prolog_success!(&mut wam, "?- bagof(X, Y^((X = 1, Y = 1; (X = 2, Y = 2))), S).",
                           [["S = [1, 2]", "X = _0", "Y = _5"]]);
    assert_prolog_success!(&mut wam, "?- bagof(X, Y^((X = 1 ; Y = 1) ; (X = 2, Y = 2)), S).",
                           [["S = [1, _126, 2]", "X = _0", "Y = _5"]]);

    assert_prolog_success!(&mut wam, "?- setof(X, Y^((X = 1, Y = 1; (X = 2, Y = 2))), S).",
                           [["S = [1, 2]", "X = _0", "Y = _5"]]);
    assert_prolog_success!(&mut wam, "?- setof(X, Y^((X = 1 ; Y = 1) ; (X = 2, Y = 2)), S).",
                           [["S = [_126, 1, 2]", "X = _0", "Y = _5"]]);
    assert_prolog_success!(&mut wam, "?- setof(X, (exists(U,V) ^ member(X, [V,U,f(U),f(V)])), [a,b,f(b),f(a)]).");

    submit(&mut wam, ":- use_module(library(non_iso)).");
    
    assert_prolog_failure!(&mut wam, "?- forall(true, false).");
    assert_prolog_success!(&mut wam, "?- forall(false, true).");
    assert_prolog_success!(&mut wam, "?- catch(forall(_, true), error(instantiation_error, _), true).");
    assert_prolog_success!(&mut wam, "?- catch(forall(true, _), error(instantiation_error, _), true).");
    assert_prolog_success!(&mut wam, "?- catch(forall(1, true), error(type_error(callable, 1), _), true).");
    assert_prolog_success!(&mut wam, "?- catch(forall(true, 1), error(type_error(callable, 1), _), true).");

    submit(&mut wam, "
:- dynamic(cat/0).
cat.

:- dynamic(dog/0).
dog :- true.

elk(X) :- moose(X).

:- dynamic(legs/2).
legs(A, 6) :- insect(A).
legs(A, 7) :- A, call(A).

:- dynamic(insect/1).
insect(ant).
insect(bee).");

    assert_prolog_success!(&mut wam, "?- clause(cat, true).");
    assert_prolog_success!(&mut wam, "?- clause(dog, true).");
    assert_prolog_success!(&mut wam, "?- clause(legs(I, 6), Body).",
                           [["I = _1", "Body = insect(_1)"]]);
    assert_prolog_success!(&mut wam, "?- clause(legs(C, 7), Body).",
                           [["C = _1", "Body = ','(_1, call(C))"]]);
    assert_prolog_success!(&mut wam, "?- clause(insect(I), T).",
                           [["I = ant", "T = true"],
                            ["I = bee", "T = true"]]);
    assert_prolog_failure!(&mut wam, "?- clause(x, Body).");
    assert_prolog_success!(&mut wam, "?- catch(clause(_, _), error(instantiation_error, _), true).");
    assert_prolog_success!(&mut wam, "?- catch(clause(4, _), error(type_error(callable, 4), _), true).");
    assert_prolog_success!(&mut wam, "?- catch(clause(elk(N), _), error(permission_error(access, private_procedure, elk/1), _), true).");
    assert_prolog_success!(&mut wam, "?- catch(clause(atom(N), _), error(permission_error(access, private_procedure, atom/1), _), true).");

    assert_prolog_success!(&mut wam, "?- asserta(legs(octopus, 8)).");
    assert_prolog_success!(&mut wam, "?- asserta( (legs(A, 4) :- animal(A)) ).");
    assert_prolog_success!(&mut wam, "?- asserta( (foo(X) :- X, call(X)) ).");
    assert_prolog_success!(&mut wam, "?- catch(asserta(_), error(instantiation_error, _), true).");
    assert_prolog_failure!(&mut wam, "?- asserta(_).");
    assert_prolog_success!(&mut wam, "?- catch(asserta(4), error(type_error(callable, 4), _), true).");
    assert_prolog_failure!(&mut wam, "?- asserta(4).");
    assert_prolog_success!(&mut wam, "?- catch(asserta( (foo :- 4) ), error(type_error(callable, 4), _), true).");
    assert_prolog_failure!(&mut wam, "?- asserta( (foo :- 4) ).");
    assert_prolog_success!(&mut wam, "?- catch(asserta( (atom(_) :- true) ), error(permission_error(modify, static_procedure, atom/1), _), true).");
    assert_prolog_failure!(&mut wam, "?- asserta( (atom(_) :- true) ).");

    submit(&mut wam, "
:- dynamic(cat/0).
cat.

:- dynamic(dog/0).
dog :- true.

elk(X) :- moose(X).

:- dynamic(legs/2).
legs(A, 6) :- insect(A).
legs(A, 7) :- A, call(A).

:- dynamic(insect/1).
insect(ant).
insect(bee).");

    assert_prolog_success!(&mut wam, "?- assertz(legs(octopus, 8)).");
    assert_prolog_success!(&mut wam, "?- assertz( (legs(A, 4) :- animal(A)) ).");
    assert_prolog_success!(&mut wam, "?- assertz( (foo(X) :- X, call(X)) ).");
    assert_prolog_success!(&mut wam, "?- catch(assertz(_), error(instantiation_error, _), true).");
    assert_prolog_failure!(&mut wam, "?- assertz(_).");
    assert_prolog_success!(&mut wam, "?- catch(assertz(4), error(type_error(callable, 4), _), true).");
    assert_prolog_failure!(&mut wam, "?- assertz(4).");
    assert_prolog_success!(&mut wam, "?- catch(assertz( (foo :- 4) ), error(type_error(callable, 4), _), true).");
    assert_prolog_failure!(&mut wam, "?- assertz( (foo :- 4) ).");
    assert_prolog_success!(&mut wam, "?- catch(assertz( (atom(_) :- true) ), error(permission_error(modify, static_procedure, atom/1), _), true).");
    assert_prolog_failure!(&mut wam, "?- assertz( (atom(_) :- true) ).");

    submit(&mut wam, "
:- dynamic(legs/2).
legs(A, 4) :- animal(A).
legs(octopus, 8).
legs(A, 6) :- insect(A).
legs(spider, 8).
legs(B, 2) :- bird(B).

:- dynamic(insect/1).
insect(ant).
insect(bee).

:- dynamic(foo/1).
foo(X) :- call(X), call(X).
foo(X) :- call(X) -> call(X).");

    assert_prolog_success!(&mut wam, "?- retract(legs(octopus, 8)).");
    assert_prolog_failure!(&mut wam, "?- retract(legs(spider, 6)).");
    assert_prolog_success!(&mut wam, "?- retract( (legs(X, 2) :- T) ).",
                           [["X = _1", "T = bird(_1)"]]);
    assert_prolog_success!(&mut wam, "?- retract( (legs(X, Y) :- Z) ).",
                           [["X = _1", "Y = 4", "Z = animal(_1)"],
                            ["X = _1", "Y = 6", "Z = insect(_1)"],
                            ["X = spider", "Y = 8", "Z = true"]]);
    assert_prolog_failure!(&mut wam, "?- retract( (legs(X, Y) :- Z) ).");
    assert_prolog_success!(&mut wam, "?- retract(insect(I)).",
                           [["I = ant"],
                            ["I = bee"]]);
    assert_prolog_success!(&mut wam, "?- retract(( foo(A) :- A, call(A) )).",
                           [["A = call(A)"]]);
    assert_prolog_success!(&mut wam, "?- foo(atom(atom)).");
    assert_prolog_success!(&mut wam, "?- retract(( foo(C) :- A -> B )).",
                           [["A = call(_1)", "B = call(_1)", "C = _1"]]);
    assert_prolog_failure!(&mut wam, "?- retract( (X :- in_eec(Y)) ).");
    assert_prolog_success!(&mut wam, "?- catch(retract( (X :- in_eec(Y)) ), error(instantiation_error, _), true).");
    assert_prolog_failure!(&mut wam, "?- retract( (4 :- X) ).");
    assert_prolog_success!(&mut wam, "?- catch(retract( (4 :- X) ), error(type_error(callable, 4), _), true).");
    assert_prolog_failure!(&mut wam, "?- retract( (atom(X) :- X == '[]') ).");
    assert_prolog_success!(&mut wam, "?- catch(retract( (atom(X) :- X == '[]') ), error(permission_error(modify, static_procedure, atom/1), _), true).");

    /* This example shows why machine::compile::localize_self_calls is necessary. */
submit(&mut wam, "
:- dynamic(p/1).

p(a).
p(b).
p(c) :- p(d).
p(d).");

    assert_prolog_success!(&mut wam, "?- p(X), retract(p(_)).",
                           [["X = a"],
                            ["X = a"],
                            ["X = a"]]);
    
    submit(&mut wam, "
:- dynamic(foo/1).
foo(X) :- call(X), call(X).
foo(X) :- call(X) -> call(X).");

    assert_prolog_success!(&mut wam, "?- abolish(foo/2).");
    assert_prolog_failure!(&mut wam, "?- abolish(foo/_).");
    assert_prolog_success!(&mut wam, "?- catch(abolish(foo/_), error(instantiation_error, abolish/1), true).");
    assert_prolog_failure!(&mut wam, "?- abolish(foo).");
    assert_prolog_success!(&mut wam, "?- catch(abolish(foo), error(type_error(predicate_indicator, foo), abolish/1), true).");
    assert_prolog_failure!(&mut wam, "?- abolish(foo(_)).");
    assert_prolog_success!(&mut wam, "?- catch(abolish(foo(_)), error(type_error(predicate_indicator, foo(_)), abolish/1), true).");
    assert_prolog_failure!(&mut wam, "?- abolish(abolish/1).");
    assert_prolog_success!(&mut wam, "?- catch(abolish(abolish/1), error(permission_error(modify, static_procedure, abolish/1), abolish/1), true).");

    assert_prolog_success!(&mut wam, "?- atom_length('enchanted evening', N).",
                           [["N = 17"]]);
    assert_prolog_success!(&mut wam, r"?- atom_length('enchanted\
 evening', N).",
                           [["N = 17"]]);
    assert_prolog_success!(&mut wam, "?- atom_length('', N).",
                           [["N = 0"]]);
    assert_prolog_failure!(&mut wam, "?- atom_length('scarlet', 5).");
    assert_prolog_success!(&mut wam, "?- catch((atom_length(Atom, 4), false), error(instantiation_error, _), true).");
    assert_prolog_success!(&mut wam, "?- catch((atom_length(1.23, 4), false), error(type_error(atom, 1.23), _), true).");
    assert_prolog_success!(&mut wam, "?- catch((atom_length(atom, '4'), false), error(type_error(integer, '4'), _), true).");

}


#[test]
fn test_queries_on_setup_call_cleanup()
{
    let mut wam = Machine::new();

    // Test examples from the ISO Prolog page for setup_call_catch.
    assert_prolog_failure!(&mut wam, "?- setup_call_cleanup(false, _, _).");
    assert_prolog_success!(&mut wam, "?- catch(setup_call_cleanup(true, throw(unthrown), _), error(instantiation_error, _), true).");
    assert_prolog_success!(&mut wam, "?- setup_call_cleanup(true, true, (true ; throw(x))).");
    assert_prolog_success!(&mut wam, "?- setup_call_cleanup(true, X = 1, X = 2).",
                           [["X = 1"]]);
    assert_prolog_success!(&mut wam, "?- setup_call_cleanup(true, true, X = 2).",
                           [["X = 2"]]);
    assert_prolog_success!(&mut wam, "?- catch(setup_call_cleanup(true, X=true, X), error(E, _), true).",
                           [["E = instantiation_error", "X = _1"]]);
    assert_prolog_success!(&mut wam, "?- catch(setup_call_cleanup(X=throw(ex), true, X), E, true).",
                           [["E = ex", "X = _3"]]);
    assert_prolog_success!(&mut wam, "?- setup_call_cleanup(true, true, false).");
    assert_prolog_success!(&mut wam, "?- setup_call_cleanup(S = 1, G = 2, C = 3).",
                           [["S = 1", "G = 2", "C = 3"]]);
    assert_prolog_success!(&mut wam, "?- setup_call_cleanup((S=1;S=2), G=3, C=4).",
                           [["S = 1", "G = 3", "C = 4"]]);
    assert_prolog_success!(&mut wam, "?- setup_call_cleanup(S=1, G=2, writeq(S+G)).",
                           [["S = 1", "G = 2"]]);
    assert_prolog_success!(&mut wam, "?- setup_call_cleanup(S=1, (G=2;G=3), writeq(S+G)).",
                           [["S = 1", "G = 2"],
                            ["S = 1", "G = 3"]]);
    assert_prolog_success!(&mut wam, "?- setup_call_cleanup(S=1, G=2, writeq(S+G>A+B)), A=3, B=4.",
                           [["S = 1", "G = 2", "A = 3", "B = 4"]]);
    assert_prolog_success!(&mut wam,
                           "?- catch(setup_call_cleanup(S=1, (G=2;G=3,throw(x)), writeq(S+G)), E, true).",
                           [["S = 1", "G = 2", "E = _26"], ["G = _4", "E = x", "S = _1"]]);
    assert_prolog_success!(&mut wam,
                           "?- setup_call_cleanup(S=1, (G=2;G=3),writeq(S+G>B)), B=4, !.",
                           [["S = 1", "B = 4", "G = 2"]]);
    assert_prolog_success!(&mut wam,
                           "?- setup_call_cleanup(S=1,G=2,writeq(S+G>B)),B=3,!.",
                           [["S = 1", "G = 2", "B = 3"]]);
    assert_prolog_success!(&mut wam,
                           "?- setup_call_cleanup(S=1,(G=2;false),writeq(S+G>B)),B=3,!.",
                           [["S = 1", "G = 2", "B = 3"]]);
    assert_prolog_success!(&mut wam,
                           "?- setup_call_cleanup(S=1,(G=2;S=2),writeq(S+G>B)), B=3, !.",
                           [["S = 1", "B = 3", "G = 2"]]);
    assert_prolog_failure!(&mut wam,
                           "?- setup_call_cleanup(S=1,(G=2;G=3), writeq(S+G>B)), B=4, !, throw(x).");

    assert_prolog_success!(&mut wam,
                           "?- catch(setup_call_cleanup(true,throw(goal),throw(cl)), Pat, true).",
                           [["Pat = goal"]]);
    assert_prolog_success!(&mut wam,
                           "?- catch(( setup_call_cleanup(true,(G=1;G=2),throw(cl)), throw(cont)), Pat, true).",
                           [["Pat = cont", "G = _1"]]);

    // fails here.
    assert_prolog_success!(&mut wam,
"?- setup_call_cleanup(true, (X=1;X=2), writeq(a)), setup_call_cleanup(true,(Y=1;Y=2),writeq(b)), !.",
                           [["Y = 1", "X = 1"]]);
}

#[test]
fn test_queries_on_call_with_inference_limit()
{
    let mut wam = Machine::new();

    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(throw(error), 0, R).",
                           [["R = inference_limit_exceeded"]]);
    assert_prolog_success!(&mut wam, "?- catch(call_with_inference_limit(throw(error), 1, R), error, true).");

    assert_prolog_failure!(&mut wam, "?- call_with_inference_limit(g(X), 5, R).");

    submit(&mut wam, "g(1). g(2). g(3). g(4). g(5).");

    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(g(X), 5, R).",
                           [["R = true", "X = 1"],
                            ["R = true", "X = 2"],
                            ["R = true", "X = 3"],
                            ["R = true", "X = 4"],
                            ["R = !", "X = 5"]]);
    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(g(X), 5, R), call(true).",
                           [["R = true", "X = 1"],
                            ["R = true", "X = 2"],
                            ["R = true", "X = 3"],
                            ["R = true", "X = 4"],
                            ["R = !", "X = 5"]]);
    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(g(X), 2, R).",
                           [["R = true", "X = 1"],
                            ["R = true", "X = 2"],
                            ["R = inference_limit_exceeded", "X = _1"]]);
    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(g(X), 3, R1),
                                         call_with_inference_limit(g(X), 5, R2).",
                           [["X = 1", "R1 = true", "R2 = !"],
                            ["X = 2", "R1 = true", "R2 = !"],
                            ["X = 3", "R1 = true", "R2 = !"],
                            ["X = 4", "R1 = true", "R2 = !"],
                            ["X = 5", "R1 = !", "R2 = !"]]);

    submit(&mut wam, "f(X) :- call_with_inference_limit(g(X), 5, _).");

    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(f(X), 7, R).",
                           [["R = true", "X = 1"],
                            ["R = true", "X = 2"],
                            ["R = true", "X = 3"],
                            ["R = true", "X = 4"],
                            ["R = !", "X = 5"]]);
    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(f(X), 6, R).",
                           [["R = true", "X = 1"],
                            ["R = true", "X = 2"],
                            ["R = true", "X = 3"],
                            ["R = true", "X = 4"],
                            ["R = inference_limit_exceeded", "X = _1"]]);
    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(f(X), 4, R).",
                           [["R = true", "X = 1"],
                            ["R = true", "X = 2"],
                            ["R = inference_limit_exceeded", "X = _1"]]);
    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(f(X), 3, R).",
                           [["R = true", "X = 1"],
                            ["R = inference_limit_exceeded", "X = _1"]]);
    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(f(X), 2, R).",
                           [["R = inference_limit_exceeded", "X = _1"]]);

    submit(&mut wam, "e(X) :- call_with_inference_limit(f(X), 10, _).");

    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(e(X), 10, R).",
                           [["R = true", "X = 1"],
                            ["R = true", "X = 2"],
                            ["R = true", "X = 3"],
                            ["R = true", "X = 4"],
                            ["R = !", "X = 5"]]);
    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(e(X), 8, R).",
                           [["R = true", "X = 1"],
                            ["R = true", "X = 2"],
                            ["R = true", "X = 3"],
                            ["R = true", "X = 4"],
                            ["R = inference_limit_exceeded", "X = _1"]]);
    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(e(X), 6, R).",
                           [["R = true", "X = 1"],
                            ["R = true", "X = 2"],
                            ["R = inference_limit_exceeded", "X = _1"]]);
    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(e(X), 5, R).",
                           [["R = true", "X = 1"],
                            ["R = inference_limit_exceeded", "X = _1"]]);
    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(e(X), 4, R).",
                           [["R = inference_limit_exceeded", "X = _1"]]);

    submit(&mut wam, "f(X, R) :- call_with_inference_limit(g(X), 5, R).");

    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(f(X, R), 4, S).",
                           [["S = true", "X = 1", "R = true"],
                            ["S = true", "X = 2", "R = true"],
                            ["S = inference_limit_exceeded", "X = _1", "R = _2"]]);
    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(f(X, R), 8, R).",
                           [["R = true", "X = 1"],
                            ["R = true", "X = 2"],
                            ["R = true", "X = 3"],
                            ["R = true", "X = 4"],
                            ["R = !", "X = 5"]]);

    submit(&mut wam, "g(1). g(2). g(3). g(4). g(5). g(6).");

    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(f(X, R), 8, S).",
                           [["R = true", "X = 1", "S = true"],
                            ["R = true", "X = 2", "S = true"],
                            ["R = true", "X = 3", "S = true"],
                            ["R = true", "X = 4", "S = true"],
                            ["R = true", "X = 5", "S = true"],
                            ["R = inference_limit_exceeded", "S = !", "X = _1"]]);
    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(g(X), 2, R), call_with_inference_limit(g(X), 1, S).",
                           [["R = true", "X = 1", "S = !"],
                            ["R = true", "X = 2", "S = !"],
                            ["R = true", "X = 3", "S = !"],
                            ["R = true", "X = 4", "S = !"],
                            ["R = true", "X = 5", "S = !"],
                            ["R = !", "X = 6", "S = !"]]);
    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(g(X), 2, R), call_with_inference_limit(g(X), 1, R).",
                           [["R = !", "X = 6"]]);
    assert_prolog_success!(&mut wam, "?- call_with_inference_limit(g(X), 1, R), call_with_inference_limit(g(X), 1, R).",
                           [["R = inference_limit_exceeded", "X = _1"]]);
}

#[test]
fn test_queries_on_dcgs()
{
    let mut wam = Machine::new();

    submit(&mut wam, ":- use_module(library(dcgs)).");

    // test case by YeGoblynQueene from hacker news.
    compile_user_module(&mut wam,
    " ability(destroy, X) --> destroy(X).
      destroy(X) --> [destroy], target(X).
      target(X) --> [target], permanent(X).
      permanent(X) --> [creature], creature(X).
      permanent(X) --> [artifact], artifact(X).
      permanent(X) --> [land], land(X).
      spell(X) --> [sorcery], sorcery(X).
      spell(X) --> [instant], instant(X).

      creature('Llanowar Elves') --> [].
      artifact('Ankh of Mishra') --> [].
      land('Mountain') --> [].
      % etc permanents
      sorcery('Duress') --> [].
      instant('Lightning Bolt') --> [].".as_bytes());

    assert_prolog_success!(&mut wam, "?- phrase(ability(destroy, X), P).",
                           [["P = [destroy, target, creature]", "X = 'Llanowar Elves'"],
                            ["P = [destroy, target, artifact]", "X = 'Ankh of Mishra'"],
                            ["P = [destroy, target, land]", "X = 'Mountain'"]]);
}

#[test]
fn test_queries_on_string_lists()
{
    let mut wam = Machine::new();

    // double_quotes is chars by default.
    assert_prolog_success!(&mut wam, "?- \"\" =@= [].");
    assert_prolog_failure!(&mut wam, "?- \"\" == [].");
    assert_prolog_failure!(&mut wam, "?- \"abc\" == [].");
    assert_prolog_success!(&mut wam, "?- \"abc\" =@= ['a', 'b', 'c'].");
    assert_prolog_success!(&mut wam, "?- \"abc\" =@= ['a', 'b', c].");
    assert_prolog_success!(&mut wam, "?- \"abc\" =@= ['a', b, 'c'].");
    assert_prolog_success!(&mut wam, "?- \"abc\" =@= [a, 'b', 'c'].");
    assert_prolog_success!(&mut wam, "?- \"abc\" =@= [a, 'b', c].");
    assert_prolog_failure!(&mut wam, "?- \"abc\" == ['a', 'b', 'c'].");
    assert_prolog_failure!(&mut wam, "?- \"abc\" == ['a', 'b', c].");
    assert_prolog_failure!(&mut wam, "?- \"abc\" == ['a', b, 'c'].");
    assert_prolog_failure!(&mut wam, "?- \"abc\" == [a, 'b', 'c'].");
    assert_prolog_failure!(&mut wam, "?- \"abc\" == [a, 'b', c].");
    assert_prolog_failure!(&mut wam, "?- \"koen\" == [k, o, e, n].");
    assert_prolog_success!(&mut wam, "?- \"koen\" = [k, o, e, n].");
    assert_prolog_success!(&mut wam, "?- \"koen\" =@= [k, o, e, n].");
    assert_prolog_success!(&mut wam, "?- \"koen\" =@= \"koen\".");
    assert_prolog_success!(&mut wam, "?- \"koen\" = [k, o | X].",
                           [["X = [e, n]"]]);
    assert_prolog_success!(&mut wam, "?- \"koen\" = [k, o | X], X = \"en\".",
                           [["X = [e, n]"]]);
    assert_prolog_failure!(&mut wam, "?- \"koen\" = [k, o | X], X == \"en\".");
    assert_prolog_success!(&mut wam, "?- \"koen\" = [k, o | X], X =@= \"en\".",
                           [["X = [e, n]"]]);

    assert_prolog_failure!(&mut wam, "?- X = \"abc\", Y = \"abc\", X == Y.");
    assert_prolog_failure!(&mut wam, "?- partial_string(\"abc\", X), partial_string(\"abc\", Y), X == Y.");

    assert_prolog_success!(&mut wam, "?- X = \"abc\", Y = \"abc\", X =@= Y.");
    assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X), partial_string(\"abc\", Y), X =@= Y.");

    submit(&mut wam, "matcher([a,b,c|X], ['d','e','f'|X]).");

    assert_prolog_success!(&mut wam, "?- matcher(\"abcdef\", \"defdef\").");
    assert_prolog_failure!(&mut wam, "?- matcher(\"abcdef\", \"defdff\").");

    assert_prolog_success!(&mut wam, "?- matcher([X, Y, Z | W], [A, B, C | W]).",
                           [["A = d", "B = e", "C = f", "W = _1", "X = a", "Y = b", "Z = c"]]);
    assert_prolog_failure!(&mut wam, "?- matcher([X, Y, Z | W], [X, B, C | W]).");

    submit(&mut wam, "matcher([a,b,c|X], X).");

    assert_prolog_success!(&mut wam, "?- matcher(\"abcdef\", X), X = [d,e,f|Y], Y =@= [], X = \"def\".",
                           [["X = [d, e, f]", "Y = []"]]);
    assert_prolog_success!(&mut wam, "?- matcher(\"abcdef\", X), X = [d,e,f|Y], Y =@= [], X =@= \"def\".",
                           [["X = [d, e, f]", "Y = []"]]);
    assert_prolog_success!(&mut wam, "?- X = ['a', 'b', 'c' | \"def\"].",
                           [["X = [a, b, c, d, e, f]"]]);

    assert_prolog_success!(&mut wam, "?- X = [a,b,c|\"abc\"].",
                           [["X = [a, b, c, a, b, c]"]]);

    assert_prolog_success!(&mut wam, "?- set_prolog_flag(double_quotes, atom).");

    assert_prolog_success!(&mut wam, "?- matcher(X, Y).",
                          [["X = [a, b, c | _1]", "Y = _1"]]);
    assert_prolog_failure!(&mut wam, "?- matcher(\"abcdef\", Y).");

    assert_prolog_success!(&mut wam, "?- set_prolog_flag(double_quotes, chars).");

    assert_prolog_success!(&mut wam, "?- X = \"abc\", X = ['a' | Y], set_prolog_flag(double_quotes, atom).",
                           [["X = \"abc\"", "Y = \"bc\""]]);

    // partial strings.
    assert_prolog_success!(&mut wam, "?- set_prolog_flag(double_quotes, chars).");

    assert_prolog_failure!(&mut wam, "?- Y = 5, partial_string(\"abc\", Y).");
    assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X).",
                           [["X = [a, b, c | _]"]]);

    assert_prolog_failure!(&mut wam, "?- partial_string(\"abc\", X), partial_string(\"abc\", Y), matcher(X, V),
                                         matcher(Y, Z), V = Z.");

    submit(&mut wam, "matcher([a, b, c | X], X).");

    assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X), matcher(X, Y).",
                           [["X = [a, b, c | _]", "Y = _"]]);
    assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X), matcher(X, Y), Y = \"def\".",
                           [["X = [a, b, c, d, e, f]", "Y = [d, e, f]"]]);
    assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X), matcher(X, Y), \"def\" = Y.",
                           [["X = [a, b, c, d, e, f]", "Y = [d, e, f]"]]);

    assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X), matcher(X, Y), partial_string(\"def\", Y).",
                           [["X = [a, b, c, d, e, f | _]",
                             "Y = [d, e, f | _]"]]);
    assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X), matcher(X, Y), partial_string(\"def\", Y),
                                         Y = \"defghijkl\".",
                           [["X = [a, b, c, d, e, f, g, h, i, j, k, l]",
                             "Y = [d, e, f, g, h, i, j, k, l]"]]);
    assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X), matcher(X, Y), partial_string(\"def\", Y),
                                         \"defghijkl\" = Y.",
                           [["X = [a, b, c, d, e, f, g, h, i, j, k, l]",
                             "Y = [d, e, f, g, h, i, j, k, l]"]]);

    assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X), matcher(X, Y), Y = [d, e, f | G].",
                           [["X = [a, b, c, d, e, f | _]", "Y = [d, e, f | _]", "G = _"]]);
    assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X), matcher(X, Y), [d, e, f | G] = Y.",
                           [["X = [a, b, c, d, e, f | _]", "Y = [d, e, f | _]", "G = _"]]);
    assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X), matcher(X, Y), Y = [d, e, f | G],
                                         G = \"ghi\".",
                           [["X = [a, b, c, d, e, f, g, h, i]", "Y = [d, e, f, g, h, i]", "G = [g, h, i]"]]);
    assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X), matcher(X, Y), Y = [d, e, f | G],
                                         is_partial_string(Y), G = \"ghi\".",
                           [["X = [a, b, c, d, e, f, g, h, i]", "Y = [d, e, f, g, h, i]", "G = [g, h, i]"]]);
    assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X), matcher(X, Y), Y = [d, e, f | G],
                                         is_partial_string(Y), is_partial_string(G), G = \"ghi\".",
                           [["X = [a, b, c, d, e, f, g, h, i]", "Y = [d, e, f, g, h, i]", "G = [g, h, i]"]]);
    assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X), partial_string(\"ababc\", Y), Y = [a,b|Z],
                                         X =@= Z.",
                           [["X = [a, b, c | _]", "Y = [a, b, a, b, c | _]", "Z = [a, b, c | _]"]]);
    assert_prolog_failure!(&mut wam, "?- partial_string(\"abc\", X), partial_string(\"ababc\", Y), Y = [a,b|Z],
                                         X == Z.");

    assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X), X @> \"abc\".");
    assert_prolog_failure!(&mut wam, "?- partial_string(\"abc\", X), X \\=@= \"abc\".");
    assert_prolog_failure!(&mut wam, "?- partial_string(\"abc\", X), X @< \"abc\".");

    assert_prolog_success!(&mut wam, "?- partial_string(\"ab\", X), matcher(X, Y), Y = [a,b|V],
                                         matcher(Y, Z), is_partial_string(Y).",
                           [["V = [c | _]", "X = [a, b, c, a, b, c | _]", "Y = [a, b, c | _]", "Z = _"]]);
    assert_prolog_success!(&mut wam, "?- partial_string(\"a\", X), matcher(X, Y).",
                           [["X = [a, b, c | _]", "Y = _"]]);
    assert_prolog_success!(&mut wam, "?- partial_string(\"a\", X), matcher(X, Y), is_partial_string(Y).",
                           [["X = [a, b, c | _]", "Y = _"]]);
    assert_prolog_success!(&mut wam, "?- partial_string(\"a\", X), matcher(X, Y), Y = \"def\".",
                           [["X = [a, b, c, d, e, f]", "Y = [d, e, f]"]]);

    submit(&mut wam, "matcher([a,b,c|X], X).
                      matcher([a,b,d|X], X).");

    assert_prolog_success!(&mut wam, "?- partial_string(\"ab\", X), matcher(X, Y).",
                           [["X = [a, b, c | _]", "Y = _"],
                            ["X = [a, b, d | _]", "Y = _"]]);

    submit(&mut wam, "matcher([a,b,c,d|X], X).
                      matcher([a,c,d|X], X).");

    assert_prolog_success!(&mut wam, "?- partial_string(\"ab\", X), matcher(X, Y).",
                           [["X = [a, b, c, d | _]", "Y = _"]]);

    assert_prolog_success!(&mut wam, "?- partial_string(\"a\", X), matcher(X, Y).",
                           [["X = [a, b, c, d | _]", "Y = _"],
                            ["X = [a, c, d | _]", "Y = _"]]);

    submit(&mut wam, "matcher([a,b,c,d|X], X).
                      matcher([a,c,d|X], X).
                      matcher([a,e,f|X], X).");

    assert_prolog_success!(&mut wam, "?- partial_string(\"a\", X), matcher(X, Y).",
                           [["X = [a, b, c, d | _]", "Y = _"],
                            ["X = [a, c, d | _]", "Y = _"],
                            ["X = [a, e, f | _]", "Y = _"]]);
    assert_prolog_success!(&mut wam, "?- partial_string(\"a\", X), matcher(X, Y), Y = \" t\".",
                           [["X = [a, b, c, d, ' ', t]", "Y = [' ', t]"],
                            ["X = [a, c, d, ' ', t]", "Y = [' ', t]"],
                            ["X = [a, e, f, ' ', t]", "Y = [' ', t]"]]);

    submit(&mut wam, "matcher([a,b,c|X], X) :- X = [].
                      matcher([a,b,c|X], X).");

    assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X), matcher(X, Y).",
                           [["X = [a, b, c]", "Y = []"],
                            ["X = [a, b, c | _]", "Y = _"]]);
    assert_prolog_success!(&mut wam, "?- partial_string(\"a\", X), matcher(X, Y).",
                           [["X = [a, b, c]", "Y = []"],
                            ["X = [a, b, c | _]", "Y = _"]]);

    assert_prolog_failure!(&mut wam, "?- partial_string(\"abc\", X), partial_string(\"bc\", Y), X = [a | Y].");

    submit(&mut wam, "matcher([a|X], X) :- matcher2(X, _).
                      matcher([b|X], X) :- matcher2(X, _).

                      matcher2([c|X], X).
                      matcher2([d|X], X).");

    assert_prolog_success!(&mut wam, "?- partial_string(\"\", X), matcher(X, Y).",
                           [["X = [a, c | _]", "Y = [c | _]"],
                            ["X = [a, d | _]", "Y = [d | _]"],
                            ["X = [b, c | _]", "Y = [c | _]"],
                            ["X = [b, d | _]", "Y = [d | _]"]]);
    assert_prolog_success!(&mut wam, "?- partial_string(\"a\", X), matcher(X, Y).",
                           [["X = [a, c | _]", "Y = [c | _]"],
                            ["X = [a, d | _]", "Y = [d | _]"]]);
    assert_prolog_success!(&mut wam, "?- partial_string(\"b\", X), matcher(X, Y).",
                           [["X = [b, c | _]", "Y = [c | _]"],
                            ["X = [b, d | _]", "Y = [d | _]"]]);
    assert_prolog_success!(&mut wam, "?- partial_string(\"bc\", X), matcher(X, Y).",
                           [["X = [b, c | _]", "Y = [c | _]"]]);

    submit(&mut wam, "f(\"appendy jones\").
                      f(\"appendy smithers jones\").
                      f(\"appendy o'toole\").");

    assert_prolog_success!(&mut wam, "?- partial_string(\"appendy\", X), f(X).",
                           [["X = [a, p, p, e, n, d, y, ' ', j, o, n, e, s]"],
                            ["X = [a, p, p, e, n, d, y, ' ', s, m, i, t, h, e, r, s, ' ', j, o, n, e, s]"],
                            ["X = [a, p, p, e, n, d, y, ' ', o, ''', t, o, o, l, e]"]]);

    assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X), partial_string(\"abcdef\", X).",
                           [["X = [a, b, c, d, e, f | _]"]]);
    assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X), partial_string(\"abcdef\", X), X = \"abcdef\".",
                           [["X = [a, b, c, d, e, f]"]]);
}

#[test]
fn test_queries_on_attributed_variables()
{
    let mut wam = Machine::new();

    submit(&mut wam, "
:- module(my_mod, []).
:- use_module(library(atts)).

:- attribute dif/1, frozen/1.");

    assert_prolog_success!(&mut wam, "?- ( put_atts(V, my_mod, dif(1)) ; put_atts(V, my_mod, dif(2)) ),
                                         get_atts(V, my_mod, L).",
                           [["L = [dif(1)]", "V = _10"],
                            ["L = [dif(2)]", "V = _10"]]);

    assert_prolog_success!(&mut wam, "?- put_atts(V, my_mod, frozen(a)),
   				       ( put_atts(V, my_mod, dif(1))
   				       ; put_atts(V, my_mod, -frozen(a)), put_atts(V, my_mod, dif(2))
   				       ; put_atts(V, my_mod, dif(different)) ),
   				       get_atts(V, my_mod, Ls).",
                           [["Ls = [frozen(a), dif(1)]", "V = _10"],
                            ["Ls = [dif(2)]", "V = _10"],
                            ["Ls = [frozen(a), dif(different)]", "V = _10"]]);

    assert_prolog_success!(&mut wam, "?- put_atts(V, my_mod, [dif(1), dif(2), frozen(a)]),
   				       ( put_atts(V, my_mod, -dif(2)); put_atts(V, my_mod, -frozen(A)) ),
   				  	 get_atts(V, my_mod, L).",
                           [["A = _71", "L = [frozen(a)]", "V = _25"],
                            ["A = _71", "L = [dif(2)]", "V = _25"]]);
    assert_prolog_success!(&mut wam, "?- put_atts(V, my_mod, [dif(1), dif(2), frozen(a), frozen(b)]),
   				       ( put_atts(V, my_mod, -dif(2)) ; put_atts(V, my_mod, -frozen(A)) ),
   				  	 get_atts(V, my_mod, L).",
                           [["A = _111", "L = [frozen(b)]", "V = _29"],
                            ["A = _111", "L = [dif(2)]", "V = _29"]]);
    assert_prolog_success!(&mut wam, "?- put_atts(V, my_mod, [dif(1), dif(2), frozen(a), frozen(b)]),
                                         get_atts(V, my_mod, -dif(1)).");
    assert_prolog_success!(&mut wam, "?- put_atts(V, my_mod, [dif(1), dif(2), frozen(a), frozen(b)]),
                                         get_atts(V, my_mod, -dif(3)).");
    assert_prolog_success!(&mut wam, "?- put_atts(V, my_mod, [dif(1), dif(2), frozen(a), frozen(b)]),
                                         get_atts(V, my_mod, dif(X)).",
                           [["X = 2", "V = _29"]]);
    assert_prolog_success!(&mut wam, "?- put_atts(V, my_mod, [dif(1), dif(2), frozen(a), frozen(b)]),
                                         put_atts(V, my_mod, -dif(A)), get_atts(V, my_mod, Ls).",
                           [["A = _112", "Ls = [frozen(b)]", "V = _29"]]);
    assert_prolog_success!(&mut wam, "?- put_atts(V, my_mod, [dif(1), frozen(a), dif(2), frozen(b)]),
                                         put_atts(V, my_mod, -dif(A)), get_atts(V, my_mod, Ls).",
                           [["A = _114", "Ls = [frozen(b)]", "V = _29"]]);

    submit(&mut wam, include_str!("./prolog/examples/minatotask.pl"));
    submit(&mut wam, ":- use_module(library(zdd)).");

    assert_prolog_failure!(&mut wam, "?- ZDD = ( X -> b(true) ; ( Y -> b(true) ; b(false) ) ),
                                         Vs = [X,Y],
                                         variables_set_zdd(Vs, ZDD),
                                         Vs = [1,1].");
    assert_prolog_success!(&mut wam, "?- ZDD = ( X -> b(true) ; ( Y -> b(true) ; b(false) ) ),
      					 Vs = [X,Y],
      					 variables_set_zdd(Vs, ZDD),
      					 X = 1.",
                           [["X = 1", "Y = 0", "Vs = [1, 0]", "ZDD = (1->b(true);0->b(true);b(false))"]]);
    assert_prolog_success!(&mut wam, "?- ZDD = ( X -> b(true) ; ( Y -> b(true) ; b(false) ) ),
      					 Vs = [X,Y],
      					 variables_set_zdd(Vs, ZDD),
      					 X = 0.",
                           [["Vs = [0, _58]", "X = 0", "Y = _58", "ZDD = (0->b(true);_58->b(true);b(false))"]]);
}