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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41
src/prolog/heap_print.rs
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@@ -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)
}
}