630 lines
23 KiB
Rust
630 lines
23 KiB
Rust
use std::cmp::Ordering;
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use std::collections::BTreeMap;
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use crate::atom_table;
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use crate::heap_iter::{stackful_post_order_iter, NonListElider};
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use crate::machine::machine_indices::VarKey;
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use crate::machine::mock_wam::CompositeOpDir;
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use crate::machine::{
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F64Offset, F64Ptr, Fixnum, Number, BREAK_FROM_DISPATCH_LOOP_LOC, LIB_QUERY_SUCCESS,
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};
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use crate::parser::ast::{Var, VarPtr};
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use crate::parser::parser::{Parser, Tokens};
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use crate::read::{write_term_to_heap, TermWriteResult};
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use dashu::{Integer, Rational};
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use indexmap::IndexMap;
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use super::{streams::Stream, Atom, AtomCell, HeapCellValue, HeapCellValueTag, Machine};
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#[cfg(test)]
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mod lib_machine_tests;
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/// Represents a leaf answer from a query.
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#[derive(Debug, Clone, PartialEq)]
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pub enum LeafAnswer {
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/// A `true` leaf answer.
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True,
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/// A `false` leaf answer.
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///
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/// This means that there are no more answers for the query.
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False,
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/// An exception leaf answer.
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Exception(Term),
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/// A leaf answer with bindings and residual goals.
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LeafAnswer {
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/// The bindings of variables in the query.
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///
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/// Can be empty.
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bindings: BTreeMap<String, Term>,
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/// Residual goals.
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///
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/// Can be empty.
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residual_goals: Vec<Term>,
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},
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}
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/// Represents a Prolog term.
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#[non_exhaustive]
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#[derive(Debug, Clone, PartialEq)]
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pub enum Term {
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/// An arbitrary precision integer.
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Integer(Integer),
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/// An arbitrary precision rational.
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Rational(Rational),
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/// A float.
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Float(f64),
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/// A Prolog atom.
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Atom(String),
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/// A Prolog string.
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///
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/// In particular, this represents Prolog lists of characters.
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String(String),
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/// A Prolog list.
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List(Vec<Term>),
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/// A Prolog compound term.
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Compound(String, Vec<Term>),
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/// A Prolog variable.
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Var(String),
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}
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impl Term {
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/// Creates an integer term.
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pub fn integer(value: impl Into<Integer>) -> Self {
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Term::Integer(value.into())
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}
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/// Creates a rational term.
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pub fn rational(value: impl Into<Rational>) -> Self {
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Term::Rational(value.into())
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}
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/// Creates a float term.
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pub fn float(value: impl Into<f64>) -> Self {
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Term::Float(value.into())
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}
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/// Creates an atom term.
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pub fn atom(value: impl Into<String>) -> Self {
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Term::Atom(value.into())
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}
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/// Creates a string term.
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///
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/// In specific, this represents a list of chars in Prolog.
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pub fn string(value: impl Into<String>) -> Self {
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Term::String(value.into())
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}
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/// Creates a list term.
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pub fn list(value: impl IntoIterator<Item = Term>) -> Self {
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Term::List(value.into_iter().collect())
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}
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/// Creates a compound term.
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pub fn compound(functor: impl Into<String>, args: impl IntoIterator<Item = Term>) -> Self {
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Term::Compound(functor.into(), args.into_iter().collect())
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}
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/// Creates a variable.
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pub fn variable(value: impl Into<String>) -> Self {
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Term::Var(value.into())
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}
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/// Creates a conjunction, giving the atom `true` if empty.
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pub fn conjunction(value: impl IntoIterator<Item = Term>) -> Self {
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Term::try_conjunction(value).unwrap_or(Term::atom("true"))
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}
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/// Creates a conjunction, giving `None` if empty.
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pub fn try_conjunction(value: impl IntoIterator<Item = Term>) -> Option<Self> {
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let mut iter = value.into_iter();
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iter.next().map(|first| {
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Term::try_conjunction(iter)
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.map(|rest| Term::compound(",", [first.clone(), rest]))
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.unwrap_or(first)
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})
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}
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/// Creates a disjunction, giving the atom `false` if empty.
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pub fn disjunction(value: impl IntoIterator<Item = Term>) -> Self {
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Term::try_disjunction(value).unwrap_or(Term::atom("false"))
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}
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/// Creates a disjunction, giving `None` if empty.
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pub fn try_disjunction(value: impl IntoIterator<Item = Term>) -> Option<Self> {
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let mut iter = value.into_iter();
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iter.next().map(|first| {
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Term::try_disjunction(iter)
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.map(|rest| Term::compound(";", [first.clone(), rest]))
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.unwrap_or(first)
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})
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}
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}
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/// This is an auxiliary function to turn a count into names of anonymous variables like _A, _B,
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/// _AB, etc...
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fn count_to_letter_code(mut count: usize) -> String {
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let mut letters = Vec::new();
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loop {
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let letter_idx = (count % 26) as u32;
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letters.push(char::from_u32('A' as u32 + letter_idx).unwrap());
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count /= 26;
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if count == 0 {
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break;
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}
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}
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letters.into_iter().chain("_".chars()).rev().collect()
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}
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impl Term {
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pub(crate) fn from_heapcell(
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machine: &mut Machine,
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heap_cell: HeapCellValue,
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var_names: &mut IndexMap<HeapCellValue, VarPtr>,
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) -> Self {
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// Adapted from MachineState::read_term_from_heap
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let mut term_stack = vec![];
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let iter = stackful_post_order_iter::<NonListElider>(
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&mut machine.machine_st.heap,
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&mut machine.machine_st.stack,
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heap_cell,
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);
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let mut anon_count: usize = 0;
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let var_ptr_cmp = |a, b| match a {
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Var::Named(name_a) => match b {
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Var::Named(name_b) => name_a.cmp(&name_b),
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_ => Ordering::Less,
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},
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_ => match b {
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Var::Named(_) => Ordering::Greater,
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_ => Ordering::Equal,
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},
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};
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for addr in iter {
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let addr = unmark_cell_bits!(addr);
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read_heap_cell!(addr,
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(HeapCellValueTag::Lis) => {
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let tail = term_stack.pop().unwrap();
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let head = term_stack.pop().unwrap();
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let list = match tail {
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Term::Atom(atom) if atom == "[]" => match head {
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Term::Atom(ref a) if a.chars().collect::<Vec<_>>().len() == 1 => {
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// Handle lists of char as strings
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Term::String(a.to_string())
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}
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_ => Term::List(vec![head]),
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},
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Term::List(elems) if elems.is_empty() => match head {
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Term::Atom(ref a) if a.chars().collect::<Vec<_>>().len() == 1 => {
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// Handle lists of char as strings
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Term::String(a.to_string())
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},
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_ => Term::List(vec![head]),
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},
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Term::List(mut elems) => {
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elems.insert(0, head);
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Term::List(elems)
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},
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Term::String(mut elems) => match head {
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Term::Atom(ref a) if a.chars().collect::<Vec<_>>().len() == 1 => {
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// Handle lists of char as strings
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elems.insert(0, a.chars().next().unwrap());
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Term::String(elems)
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},
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_ => {
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let mut elems: Vec<Term> = elems
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.chars()
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.map(|x| Term::Atom(x.into()))
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.collect();
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elems.insert(0, head);
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Term::List(elems)
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}
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},
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_ => {
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Term::Compound(".".into(), vec![head, tail])
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}
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};
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term_stack.push(list);
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}
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(HeapCellValueTag::Var | HeapCellValueTag::AttrVar | HeapCellValueTag::StackVar) => {
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let var = var_names.get(&addr).map(|x| x.borrow().clone());
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match var {
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Some(Var::Named(name)) => term_stack.push(Term::Var(name)),
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_ => {
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let anon_name = loop {
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// Generate a name for the anonymous variable
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let anon_name = count_to_letter_code(anon_count);
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// Find if this name is already being used
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var_names.sort_by(|_, a, _, b| {
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var_ptr_cmp(a.borrow().clone(), b.borrow().clone())
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});
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let binary_result = var_names.binary_search_by(|_,a| {
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let var_ptr = Var::Named(anon_name.clone());
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var_ptr_cmp(a.borrow().clone(), var_ptr.clone())
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});
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match binary_result {
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Ok(_) => anon_count += 1, // Name already used
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Err(_) => {
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// Name not used, assign it to this variable
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let var_ptr = VarPtr::from(Var::Named(anon_name.clone()));
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var_names.insert(addr, var_ptr);
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break anon_name;
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},
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}
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};
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term_stack.push(Term::Var(anon_name));
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},
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}
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}
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(HeapCellValueTag::F64, f) => {
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term_stack.push(Term::Float((*f).into()));
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}
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(HeapCellValueTag::Char, c) => {
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term_stack.push(Term::Atom(c.into()));
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}
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(HeapCellValueTag::Fixnum, n) => {
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term_stack.push(Term::Integer(n.into()));
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}
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(HeapCellValueTag::Cons) => {
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match Number::try_from(addr) {
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Ok(Number::Integer(i)) => term_stack.push(Term::Integer((*i).clone())),
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Ok(Number::Rational(r)) => term_stack.push(Term::Rational((*r).clone())),
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_ => {}
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}
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}
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(HeapCellValueTag::CStr, s) => {
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term_stack.push(Term::String(s.as_str().to_string()));
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}
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(HeapCellValueTag::Atom, (name, arity)) => {
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//let h = iter.focus().value() as usize;
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//let mut arity = arity;
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// Not sure why/if this is needed.
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// Might find out with better testing later.
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/*
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if iter.heap.len() > h + arity + 1 {
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let value = iter.heap[h + arity + 1];
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if let Some(idx) = get_structure_index(value) {
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// in the second condition, arity == 0,
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// meaning idx cannot pertain to this atom
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// if it is the direct subterm of a larger
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// structure.
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if arity > 0 || !iter.direct_subterm_of_str(h) {
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term_stack.push(
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Term::Literal(Cell::default(), Literal::CodeIndex(idx))
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);
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arity += 1;
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}
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}
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}
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*/
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if arity == 0 {
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let atom_name = name.as_str().to_string();
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if atom_name == "[]" {
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term_stack.push(Term::List(vec![]));
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} else {
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term_stack.push(Term::Atom(atom_name));
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}
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} else {
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let subterms = term_stack
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.drain(term_stack.len() - arity ..)
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.collect();
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term_stack.push(Term::Compound(name.as_str().to_string(), subterms));
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}
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}
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(HeapCellValueTag::PStr, atom) => {
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let tail = term_stack.pop().unwrap();
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match tail {
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Term::Atom(atom) => {
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if atom == "[]" {
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term_stack.push(Term::String(atom.as_str().to_string()));
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}
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},
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Term::List(l) => {
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let mut list: Vec<Term> = atom
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.as_str()
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.to_string()
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.chars()
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.map(|x| Term::Atom(x.to_string()))
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.collect();
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list.extend(l.into_iter());
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term_stack.push(Term::List(list));
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},
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_ => {
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let mut list: Vec<Term> = atom
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.as_str()
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.to_string()
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.chars()
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.map(|x| Term::Atom(x.to_string()))
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.collect();
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let mut partial_list = Term::Compound(
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".".into(),
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vec![
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list.pop().unwrap(),
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tail,
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],
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);
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while let Some(last) = list.pop() {
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partial_list = Term::Compound(
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".".into(),
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vec![
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last,
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partial_list,
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],
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);
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}
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term_stack.push(partial_list);
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}
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}
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}
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// I dont know if this is needed here.
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/*
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(HeapCellValueTag::PStrLoc, h) => {
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let atom = cell_as_atom_cell!(iter.heap[h]).get_name();
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let tail = term_stack.pop().unwrap();
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term_stack.push(Term::PartialString(
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Cell::default(),
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atom.as_str().to_owned(),
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Box::new(tail),
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));
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}
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*/
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_ => {
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}
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);
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}
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debug_assert_eq!(term_stack.len(), 1);
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term_stack.pop().unwrap()
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}
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}
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/// An iterator though the leaf answers of a query.
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pub struct QueryState<'a> {
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machine: &'a mut Machine,
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term: TermWriteResult,
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stub_b: usize,
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var_names: IndexMap<HeapCellValue, VarPtr>,
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called: bool,
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}
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impl Drop for QueryState<'_> {
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fn drop(&mut self) {
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// This may be wrong if the iterator is not fully consumend, but from testing it seems
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// fine.
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self.machine.trust_me();
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}
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}
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impl Iterator for QueryState<'_> {
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type Item = Result<LeafAnswer, String>;
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fn next(&mut self) -> Option<Self::Item> {
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let var_names = &mut self.var_names;
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let term_write_result = &self.term;
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let machine = &mut self.machine;
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// No more choicepoints, end iteration
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if self.called && machine.machine_st.b <= self.stub_b {
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return None;
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}
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machine.dispatch_loop();
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self.called = true;
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if !machine.machine_st.ball.stub.is_empty() {
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// NOTE: this means an exception was thrown, at which
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// point we backtracked to the stub choice point.
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// this should halt the search for solutions as it
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// does in the Scryer top-level. the exception term is
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// contained in self.machine_st.ball.
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let error_string = self
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.machine
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.machine_st
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.ball
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.stub
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.iter()
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.filter(|h| {
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matches!(
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h.get_tag(),
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HeapCellValueTag::Atom | HeapCellValueTag::Fixnum
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)
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})
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.map(|h| match h.get_tag() {
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HeapCellValueTag::Atom => {
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let (name, _) = cell_as_atom_cell!(h).get_name_and_arity();
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name.as_str().to_string()
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}
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HeapCellValueTag::Fixnum => h.get_value().clone().to_string(),
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_ => unreachable!(),
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})
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.collect::<Vec<String>>()
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.join(" ");
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return Some(Err(error_string));
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}
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if machine.machine_st.p == LIB_QUERY_SUCCESS {
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if term_write_result.var_dict.is_empty() {
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self.machine.machine_st.backtrack();
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return Some(Ok(LeafAnswer::True));
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}
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} else if machine.machine_st.p == BREAK_FROM_DISPATCH_LOOP_LOC {
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return Some(Ok(LeafAnswer::False));
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}
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let mut bindings: BTreeMap<String, Term> = BTreeMap::new();
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let var_dict = &term_write_result.var_dict;
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for (var_key, term_to_be_printed) in var_dict.iter() {
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let mut var_name = var_key.to_string();
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if var_name.starts_with('_') {
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let should_print = var_names.values().any(|x| match x.borrow().clone() {
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Var::Named(v) => v == var_name,
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_ => false,
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});
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if !should_print {
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continue;
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}
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}
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let mut term =
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Term::from_heapcell(machine, *term_to_be_printed, &mut var_names.clone());
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if let Term::Var(ref term_str) = term {
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if *term_str == var_name {
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continue;
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}
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// Var dict is in the order things appear in the query. If var_name appears
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// after term in the query, switch their places.
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let var_name_idx = var_dict
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.get_index_of(&VarKey::VarPtr(Var::Named(var_name.clone()).into()))
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.unwrap();
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let term_idx =
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var_dict.get_index_of(&VarKey::VarPtr(Var::Named(term_str.clone()).into()));
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if let Some(idx) = term_idx {
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if idx < var_name_idx {
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let new_term = Term::Var(var_name);
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let new_var_name = term_str.into();
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term = new_term;
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var_name = new_var_name;
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}
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}
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}
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bindings.insert(var_name, term);
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}
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// NOTE: there are outstanding choicepoints, backtrack
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// through them for further solutions. if
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// self.machine_st.b == stub_b we've backtracked to the stub
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// choice point, so we should break.
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self.machine.machine_st.backtrack();
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Some(Ok(LeafAnswer::LeafAnswer {
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bindings,
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residual_goals: vec![],
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}))
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}
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}
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impl Machine {
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/// Loads a module into the [`Machine`] from a string.
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pub fn load_module_string(&mut self, module_name: &str, program: impl Into<String>) {
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let stream = Stream::from_owned_string(program.into(), &mut self.machine_st.arena);
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self.load_file(module_name, stream);
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}
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|
|
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/// Consults a module into the [`Machine`] from a string.
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pub fn consult_module_string(&mut self, module_name: &str, program: impl Into<String>) {
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let stream = Stream::from_owned_string(program.into(), &mut self.machine_st.arena);
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|
self.machine_st.registers[1] = stream_as_cell!(stream);
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|
self.machine_st.registers[2] = atom_as_cell!(&atom_table::AtomTable::build_with(
|
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&self.machine_st.atom_tbl,
|
|
module_name
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|
));
|
|
|
|
self.run_module_predicate(atom!("loader"), (atom!("consult_stream"), 2));
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|
}
|
|
|
|
fn allocate_stub_choice_point(&mut self) {
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|
// NOTE: create a choice point to terminate the dispatch_loop
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|
// if an exception is thrown.
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|
|
|
let stub_b = self.machine_st.stack.allocate_or_frame(0);
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|
let or_frame = self.machine_st.stack.index_or_frame_mut(stub_b);
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|
|
|
or_frame.prelude.num_cells = 0;
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|
or_frame.prelude.e = 0;
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|
or_frame.prelude.cp = 0;
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|
or_frame.prelude.b = 0;
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|
or_frame.prelude.bp = BREAK_FROM_DISPATCH_LOOP_LOC;
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|
or_frame.prelude.boip = 0;
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|
or_frame.prelude.biip = 0;
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|
or_frame.prelude.tr = 0;
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|
or_frame.prelude.h = 0;
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|
or_frame.prelude.b0 = 0;
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|
or_frame.prelude.attr_var_queue_len = 0;
|
|
|
|
self.machine_st.b = stub_b;
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|
self.machine_st.hb = self.machine_st.heap.len();
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|
self.machine_st.block = stub_b;
|
|
}
|
|
|
|
/// Runs a query.
|
|
pub fn run_query(&mut self, query: impl Into<String>) -> QueryState {
|
|
let mut parser = Parser::new(
|
|
Stream::from_owned_string(query.into(), &mut self.machine_st.arena),
|
|
&mut self.machine_st,
|
|
);
|
|
let op_dir = CompositeOpDir::new(&self.indices.op_dir, None);
|
|
let term = parser
|
|
.read_term(&op_dir, Tokens::Default)
|
|
.expect("Failed to parse query");
|
|
|
|
self.allocate_stub_choice_point();
|
|
|
|
// Write parsed term to heap
|
|
let term_write_result =
|
|
write_term_to_heap(&term, &mut self.machine_st.heap, &self.machine_st.atom_tbl)
|
|
.expect("couldn't write term to heap");
|
|
|
|
let var_names: IndexMap<_, _> = term_write_result
|
|
.var_dict
|
|
.iter()
|
|
.map(|(var_key, cell)| match var_key {
|
|
// NOTE: not the intention behind Var::InSitu here but
|
|
// we can hijack it to store anonymous variables
|
|
// without creating problems.
|
|
VarKey::AnonVar(h) => (*cell, VarPtr::from(Var::InSitu(*h))),
|
|
VarKey::VarPtr(var_ptr) => (*cell, var_ptr.clone()),
|
|
})
|
|
.collect();
|
|
|
|
// Write term to heap
|
|
self.machine_st.registers[1] = self.machine_st.heap[term_write_result.heap_loc];
|
|
|
|
self.machine_st.cp = LIB_QUERY_SUCCESS; // BREAK_FROM_DISPATCH_LOOP_LOC;
|
|
let call_index_p = self
|
|
.indices
|
|
.code_dir
|
|
.get(&(atom!("call"), 1))
|
|
.expect("couldn't get code index")
|
|
.local()
|
|
.unwrap();
|
|
|
|
self.machine_st.execute_at_index(1, call_index_p);
|
|
|
|
let stub_b = self.machine_st.b;
|
|
QueryState {
|
|
machine: self,
|
|
term: term_write_result,
|
|
stub_b,
|
|
var_names,
|
|
called: false,
|
|
}
|
|
}
|
|
}
|