rishi/scryer-prolog
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properly handle cyclic terms in the printer.

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This commit is contained in:
Mark Thom
2018-05-05 12:33:29 -06:00
parent d6495c8195
commit 81a199836d
5 changed files with 113 additions and 91 deletions
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87
src/prolog/copier.rs
View File

@@ -4,6 +4,14 @@ use prolog::ast::*;
use std::collections::HashMap;
use std::ops::IndexMut;
pub type Trail = Vec<(Ref, HeapCellValue)>;
pub struct RedirectInfo {
trail: Trail,
list_redirect: HashMap<usize, usize>,
offset: usize
}
// allows us to reconstruct a HeapVarDict by relating variables
// in an existing HeapVarDict to the ones created in fn duplicate_term.
// It is used to create meaningful error reports at the toplevel.
@@ -13,9 +21,11 @@ impl CellRedirect {
pub fn new() -> Self {
CellRedirect(HashMap::new())
}
}
pub type Trail = Vec<(Ref, HeapCellValue)>;
pub fn clear(&mut self) {
self.0.clear();
}
}
pub trait CopierTarget
{
@@ -26,49 +36,60 @@ pub trait CopierTarget
fn deref(&self, Addr) -> Addr;
fn stack(&mut self) -> &mut AndStack;
fn compile_redirect(&mut self, trail: Trail, list_redirect: HashMap<usize, usize>, old_h: usize)
-> CellRedirect
where Self: IndexMut<usize, Output=HeapCellValue>
// unwind the trail *and* compute a cell redirection table.
fn unwind_and_redirect(&mut self, redirect: RedirectInfo) -> CellRedirect
where Self: IndexMut<usize, Output=HeapCellValue>
{
let mut cell_redirect: HashMap<Addr, Addr> = HashMap::new();
for (r, hcv) in trail {
for (r, hcv) in redirect.trail {
let addr = Addr::from(r);
match r {
Ref::HeapCell(hc) => {
cell_redirect.insert(addr, self[hc].as_addr(hc) - old_h);
self[hc] = hcv;
Ref::HeapCell(h) => {
cell_redirect.insert(addr, self[h].as_addr(h) - redirect.offset);
self[h] = hcv;
},
Ref::StackCell(fr, sc) => {
cell_redirect.insert(addr, self.stack()[fr][sc].clone() - old_h);
cell_redirect.insert(addr, self.stack()[fr][sc].clone() - redirect.offset);
self.stack()[fr][sc] = hcv.as_addr(0);
}
}
};
}
for (l, h) in list_redirect {
cell_redirect.insert(Addr::Lis(l), Addr::Lis(h - old_h));
for (l, h) in redirect.list_redirect {
cell_redirect.insert(Addr::Lis(l), Addr::Lis(h - redirect.offset));
}
CellRedirect(cell_redirect)
}
// duplicate_term(L1, L2) uses Cheney's algorithm to copy the term
fn unwind_trail(&mut self, redirect: RedirectInfo)
where Self: IndexMut<usize, Output=HeapCellValue>
{
for (r, hcv) in redirect.trail {
match r {
Ref::HeapCell(hc) => self[hc] = hcv.clone(),
Ref::StackCell(fr, sc) => self.stack()[fr][sc] = hcv.as_addr(0)
}
}
}
// duplicate_term_impl(L1, L2) uses Cheney's algorithm to copy the term
// at L1 to L2. trail is kept to restore the innards of L1 after
// it's been copied to L2.
fn duplicate_term(&mut self, addr: Addr) -> CellRedirect
fn duplicate_term_impl(&mut self, addr: Addr) -> RedirectInfo
where Self: IndexMut<usize, Output=HeapCellValue>
{
let mut trail = Trail::new();
let mut scan = self.source();
let old_h = self.threshold();
let mut scan = self.source();
let old_h = self.threshold();
// Lists have a compressed representation as structures,
// removing the need for NamedStr, so we use a redirection
// table for copying lists.
let mut list_redirect = HashMap::new();
self.push(HeapCellValue::Addr(addr));
while scan < self.threshold() {
@@ -84,15 +105,15 @@ pub trait CopierTarget
continue;
}
list_redirect.insert(a, self.threshold());
list_redirect.insert(a, self.threshold());
self[scan] = HeapCellValue::Addr(Addr::Lis(self.threshold()));
let hcv = self[a].clone();
self.push(hcv);
let hcv = self[a+1].clone();
self.push(hcv);
scan += 1;
},
Addr::HeapCell(_) | Addr::StackCell(_, _) => {
@@ -152,6 +173,20 @@ pub trait CopierTarget
}
}
self.compile_redirect(trail, list_redirect, old_h)
RedirectInfo { trail, list_redirect, offset: old_h }
}
fn duplicate_term_and_redirect(&mut self, addr: Addr) -> CellRedirect
where Self: IndexMut<usize, Output=HeapCellValue>
{
let redirect = self.duplicate_term_impl(addr);
self.unwind_and_redirect(redirect)
}
fn duplicate_term(&mut self, addr: Addr)
where Self: IndexMut<usize, Output=HeapCellValue>
{
let redirect = self.duplicate_term_impl(addr);
self.unwind_trail(redirect);
}
}

41
src/prolog/heap_print.rs
View File

@@ -169,7 +169,7 @@ impl<'a, Formatter: HCValueFormatter, Outputter: HCValueOutputter>
-> Self
{
let mut printer = Self::new(machine_st, fmt, output);
printer.heap_locs = Cow::Borrowed(heap_locs);
printer
}
@@ -184,10 +184,20 @@ impl<'a, Formatter: HCValueFormatter, Outputter: HCValueOutputter>
let addr = machine_st.store(machine_st.deref(addr.clone()));
printer.printed_vars.insert(addr.clone());
}
printer
}
fn print_offset(&mut self, addr: Addr) {
match addr {
Addr::HeapCell(h) | Addr::Lis(h) =>
self.outputter.append(format!("_{}", h).as_str()),
Addr::StackCell(fr, sc) =>
self.outputter.append(format!("s_{}_{}", fr, sc).as_str()),
_ => {}
}
}
// returns a HeapCellValue iff the next element to come hasn't been seen previously.
fn check_for_seen(&mut self, iter: &mut HCPreOrderIterator) -> Option<HeapCellValue> {
iter.stack().last().cloned().and_then(|addr| {
@@ -207,13 +217,16 @@ impl<'a, Formatter: HCValueFormatter, Outputter: HCValueOutputter>
}
}
// addr is not the address of a named variable. If it is a variable,
// it must be anonymous.
if addr.is_ref() {
self.outputter.append("_");
iter.stack().pop();
None
if self.machine_st.is_cyclic_term(addr.clone()) {
if self.printed_vars.contains(&addr) {
iter.stack().pop();
self.print_offset(addr);
None
} else {
self.printed_vars.insert(addr);
iter.next()
}
} else {
iter.next()
}
@@ -226,7 +239,7 @@ impl<'a, Formatter: HCValueFormatter, Outputter: HCValueOutputter>
Some(heap_val) => heap_val,
_ => return
};
match heap_val {
HeapCellValue::NamedStr(arity, name, fixity) => {
let ct = ClauseType::from(name, arity, fixity);
@@ -249,11 +262,7 @@ impl<'a, Formatter: HCValueFormatter, Outputter: HCValueOutputter>
self.state_stack.push(TokenOrRedirect::OpenList(cell));
},
HeapCellValue::Addr(Addr::HeapCell(h)) =>
self.outputter.append(format!("_{}", h).as_str()),
HeapCellValue::Addr(Addr::StackCell(fr, sc)) =>
self.outputter.append(format!("s_{}_{}", fr, sc).as_str()),
HeapCellValue::Addr(Addr::Str(_)) => {}
HeapCellValue::Addr(addr) => self.print_offset(addr)
}
}

33
src/prolog/machine/machine_state_impl.rs
View File

@@ -1121,10 +1121,9 @@ impl MachineState {
diff
}
pub(super) fn is_cyclic_term(&self, addr: Addr) -> bool {
pub(crate) fn is_cyclic_term(&self, addr: Addr) -> bool {
let mut seen = HashSet::new();
let mut fail = false;
let mut iter = self.pre_order_iter(addr);
loop {
@@ -1188,26 +1187,7 @@ impl MachineState {
self.p += 1;
}
// everything in self.redirect is potentially offset on the heap by 'offset',
// so correct for that when building the HeapVarDict.
pub(super) fn reconstruct_dict(&self, heap_locs: &HeapVarDict, offset: usize) -> HeapVarDict
{
let mut dest_heap_locs = HeapVarDict::new();
'outer:
for (orig_addr, addr) in self.redirect.0.iter() {
for (var, var_addr) in heap_locs.iter() {
if orig_addr == &self.store(self.deref(var_addr.clone())) {
dest_heap_locs.insert(var.clone(), addr.clone() + offset);
continue 'outer;
}
}
}
dest_heap_locs
}
pub(super) fn compare_term(&mut self, qt: CompareTermQT) {
let a1 = self[temp_v!(1)].clone();
let a2 = self[temp_v!(2)].clone();
@@ -1638,12 +1618,11 @@ impl MachineState {
let addr = self[temp_v!(1)].clone();
self.ball.boundary = self.heap.h;
let cell_redirect = {
self.redirect = {
let mut duplicator = DuplicateBallTerm::new(self);
duplicator.duplicate_term(addr)
duplicator.duplicate_term_and_redirect(addr)
};
self.redirect.0.extend(cell_redirect.0.into_iter());
self.p += 1;
},
&BuiltInInstruction::SetCutPoint(r) =>
@@ -2354,6 +2333,6 @@ impl MachineState {
self.block = 0;
self.ball.reset();
self.redirect.0.clear();
self.redirect.clear();
}
}

3
src/prolog/machine/mod.rs
View File

@@ -375,8 +375,7 @@ impl Machine {
if self.ms.ball.stub.len() > 0 {
let h = self.ms.heap.h;
self.ms.copy_and_align_ball_to_heap();
let heap_locs = self.ms.reconstruct_dict(heap_locs, h);
let error_str = self.ms.print_exception(Addr::HeapCell(h),
&heap_locs,
TermFormatter {},