rishi/scryer-prolog
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enable backtracking on partial strings

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This commit is contained in:
Mark Thom
2018-09-24 22:24:23 -06:00
parent 23eed192e9
commit 58ed374363
6 changed files with 205 additions and 64 deletions
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143
src/prolog/machine/machine_state_impl.rs
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@@ -49,7 +49,8 @@ impl MachineState {
or_stack: OrStack::new(),
registers: vec![Addr::HeapCell(0); MAX_ARITY + 1], // self.registers[0] is never used.
trail: vec![],
partial_string_trail: vec![],
pstr_trail: vec![],
pstr_tr: 0,
tr: 0,
hb: 0,
block: 0,
@@ -162,6 +163,51 @@ impl MachineState {
printer.print(addr)
}
pub(super)
fn unify_string(&mut self, pdl: &mut Vec<Addr>, s1: &mut StringList, s2: &mut StringList) -> bool
{
if let Some(c1) = s1.head() {
if let Some(c2) = s2.head() {
if c1 == c2 {
pdl.push(Addr::Con(Constant::String(s1.tail())));
pdl.push(Addr::Con(Constant::String(s2.tail())));
return true;
}
} else if s2.is_expandable() {
self.pstr_trail(s2.clone());
pdl.push(Addr::Con(Constant::String(s2.push_char(c1))));
pdl.push(Addr::Con(Constant::String(s1.tail())));
return true;
}
} else if s1.is_expandable() {
if let Some(c) = s2.head() {
self.pstr_trail(s1.clone());
pdl.push(Addr::Con(Constant::String(s1.push_char(c))));
pdl.push(Addr::Con(Constant::String(s2.tail())));
} else if s2.is_expandable() {
return s1 == s2;
} else {
self.pstr_trail(s1.clone());
s1.set_non_expandable();
}
return true;
} else if s2.head().is_none() {
if s2.is_expandable() {
self.pstr_trail(s2.clone());
}
s2.set_non_expandable();
return true;
}
false
}
pub(super) fn unify(&mut self, a1: Addr, a2: Addr) {
let mut pdl = vec![a1, a2];
@@ -208,6 +254,8 @@ impl MachineState {
continue;
} else if s.is_expandable() {
let prev_s = s.clone();
let mut stepper = |c| {
let new_s = s.push_char(c);
@@ -217,12 +265,14 @@ impl MachineState {
match self.heap[a1].clone() {
HeapCellValue::Addr(Addr::Con(Constant::Char(c))) => {
self.pstr_trail(prev_s);
stepper(c);
continue;
},
HeapCellValue::Addr(Addr::Con(Constant::Atom(ref a, _))) =>
if let Some(c) = a.as_str().chars().next() {
if c.len_utf8() == a.as_str().len() {
self.pstr_trail(prev_s);
stepper(c);
continue;
}
@@ -237,6 +287,7 @@ impl MachineState {
| (Addr::Con(Constant::String(ref s)), Addr::Con(Constant::EmptyList))
if self.flags.double_quotes.is_chars() => {
if s.is_expandable() && s.is_empty() {
self.pstr_trail(s.clone());
s.set_non_expandable();
continue;
}
@@ -251,43 +302,9 @@ impl MachineState {
pdl.push(Addr::HeapCell(a2 + 1));
},
(Addr::Con(Constant::String(ref mut s1)),
Addr::Con(Constant::String(ref mut s2))) => {
let mut stepper = |s1: &mut StringList, s2: &mut StringList| -> bool {
if let Some(c1) = s1.head() {
if let Some(c2) = s2.head() {
if c1 == c2 {
pdl.push(Addr::Con(Constant::String(s1.tail())));
pdl.push(Addr::Con(Constant::String(s2.tail())));
return true;
}
} else if s2.is_expandable() {
pdl.push(Addr::Con(Constant::String(s2.push_char(c1))));
pdl.push(Addr::Con(Constant::String(s1.tail())));
return true;
}
} else if s1.is_expandable() {
if let Some(c) = s2.head() {
pdl.push(Addr::Con(Constant::String(s1.push_char(c))));
pdl.push(Addr::Con(Constant::String(s2.tail())));
} else if s2.is_expandable() {
return s1 == s2;
} else {
s1.set_non_expandable();
}
return true;
} else if s2.head().is_none() {
s2.set_non_expandable();
return true;
}
false
};
self.fail = !(stepper(s1, s2) || stepper(s2, s1));
},
Addr::Con(Constant::String(ref mut s2))) =>
self.fail = !(self.unify_string(&mut pdl, s1, s2)
|| self.unify_string(&mut pdl, s2, s1)),
(Addr::Con(ref c1), Addr::Con(ref c2)) =>
if c1 != c2 {
self.fail = true;
@@ -317,6 +334,19 @@ impl MachineState {
}
}
#[inline]
fn pstr_trail(&mut self, s: StringList) {
if let Some((prev_b, prev_s, _)) = self.pstr_trail.last().cloned() {
if prev_b == self.b && prev_s == s {
return;
}
}
let len = s.len();
self.pstr_trail.push((self.b, s, len));
self.pstr_tr += 1;
}
fn trail(&mut self, r: Ref) {
match r {
Ref::HeapCell(hc) =>
@@ -356,6 +386,35 @@ impl MachineState {
}
}
pub(super) fn unwind_pstr_trail(&mut self, a1: usize, a2: usize) {
for i in a1 .. a2 {
let (_, mut s, end) = self.pstr_trail[i].clone();
s.truncate(end);
}
}
pub(super) fn tidy_pstr_trail(&mut self) {
if self.b == 0 {
return;
}
let b = self.b - 1;
let mut i = self.or_stack[b].pstr_tr;
while i < self.pstr_tr {
let str_b = self.pstr_trail[i].0;
if b < str_b {
let pstr_tr = self.pstr_tr;
let val = self.pstr_trail[pstr_tr - 1].clone();
self.pstr_trail[i] = val;
self.pstr_tr -= 1;
} else {
i += 1;
}
}
}
pub(super) fn tidy_trail(&mut self) {
if self.b == 0 {
return;
@@ -402,6 +461,8 @@ impl MachineState {
#[inline]
fn write_char_to_string(&mut self, s: &mut StringList, c: char) -> bool {
self.pstr_trail(s.clone());
let new_s = s.push_char(c);
self.heap.push(HeapCellValue::Addr(Addr::Con(Constant::String(new_s))));
false
@@ -422,6 +483,7 @@ impl MachineState {
Constant::EmptyList if self.flags.double_quotes.is_chars() =>
!s.is_empty(),
Constant::String(ref s2) if s.is_empty() && s.is_expandable() => {
self.pstr_trail(s.clone());
s.append(s2);
false
},
@@ -2140,6 +2202,7 @@ impl MachineState {
self.b,
self.p.clone() + 1,
self.tr,
self.pstr_tr,
self.heap.h,
self.b0,
self.num_of_args);
@@ -2175,6 +2238,7 @@ impl MachineState {
self.b,
self.p.clone() + offset,
self.tr,
self.pstr_tr,
self.heap.h,
self.b0,
self.num_of_args);
@@ -2246,13 +2310,14 @@ impl MachineState {
self.b0 = 0;
self.s = 0;
self.tr = 0;
self.pstr_tr = 0;
self.p = CodePtr::default();
self.cp = LocalCodePtr::default();
self.num_of_args = 0;
self.fail = false;
self.trail.clear();
self.partial_string_trail.clear();
self.pstr_trail.clear();
self.heap.clear();
self.mode = MachineMode::Write;
self.and_stack.clear();