rishi/scryer-prolog
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add TrailRef type for trail

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This commit is contained in:
Mark Thom
2019-01-26 20:06:27 -07:00
parent 91b85db90c
commit 6e735bc2d4
3 changed files with 49 additions and 23 deletions
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54
src/prolog/machine/machine_state_impl.rs
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@@ -109,16 +109,16 @@ impl MachineState {
self.heap[h] = HeapCellValue::Addr(t2)
};
self.trail(r1);
self.trail(TrailRef::from(r1));
} else {
match a2.as_var() {
Some(Ref::StackCell(fr, sc)) => {
self.and_stack[fr][sc] = t1;
self.trail(Ref::StackCell(fr, sc));
self.trail(TrailRef::StackCell(fr, sc));
},
Some(Ref::HeapCell(h)) => {
self.heap[h] = HeapCellValue::Addr(t1);
self.trail(Ref::HeapCell(h));
self.trail(TrailRef::HeapCell(h));
},
None => {}
}
@@ -347,14 +347,19 @@ impl MachineState {
self.pstr_tr += 1;
}
fn trail(&mut self, r: Ref) {
fn trail(&mut self, r: TrailRef) {
match r {
Ref::HeapCell(hc) =>
if hc < self.hb {
self.trail.push(r);
TrailRef::HeapCell(h) =>
if h < self.hb {
self.trail.push(TrailRef::HeapCell(h));
self.tr += 1;
},
Ref::StackCell(fr, _) => {
TrailRef::AttrVarLink(h, prev_addr) =>
if h < self.hb {
self.trail.push(TrailRef::AttrVarLink(h, prev_addr));
self.tr += 1;
},
TrailRef::StackCell(fr, sc) => {
let fr_gi = self.and_stack[fr].global_index;
let b_gi = if !self.or_stack.is_empty() {
if self.b > 0 {
@@ -368,7 +373,7 @@ impl MachineState {
};
if fr_gi < b_gi {
self.trail.push(r);
self.trail.push(TrailRef::StackCell(fr, sc));
self.tr += 1;
}
}
@@ -376,12 +381,17 @@ impl MachineState {
}
pub(super) fn unwind_trail(&mut self, a1: usize, a2: usize) {
for i in a1 .. a2 {
match self.trail[i] {
Ref::HeapCell(r) =>
self.heap[r] = HeapCellValue::Addr(Addr::HeapCell(r)),
Ref::StackCell(fr, sc) =>
self.and_stack[fr][sc] = Addr::StackCell(fr, sc)
// the sequence is reversed to respect the chronology of trail
// additions, now that deleted attributes can be undeleted by
// backtracking.
for i in (a1 .. a2).rev() {
match self.trail[i].clone() {
TrailRef::HeapCell(h) =>
self.heap[h] = HeapCellValue::Addr(Addr::HeapCell(h)),
TrailRef::StackCell(fr, sc) =>
self.and_stack[fr][sc] = Addr::StackCell(fr, sc),
TrailRef::AttrVarLink(h, prev_addr) =>
self.heap[h] = HeapCellValue::Addr(prev_addr)
}
}
}
@@ -424,21 +434,21 @@ impl MachineState {
let mut i = self.or_stack[b].tr;
while i < self.tr {
let tr_i = self.trail[i];
let tr_i = self.trail[i].clone();
let hb = self.hb;
match tr_i {
Ref::HeapCell(tr_i) =>
TrailRef::HeapCell(tr_i) | TrailRef::AttrVarLink(tr_i, _) =>
if tr_i < hb {
i += 1;
} else {
let tr = self.tr;
let val = self.trail[tr - 1];
let val = self.trail[tr - 1].clone();
self.trail[i] = val;
self.trail.pop();
self.tr -= 1;
},
Ref::StackCell(fr, _) => {
TrailRef::StackCell(fr, _) => {
let b = self.b - 1;
let fr_gi = self.and_stack[fr].global_index;
let b_gi = if !self.or_stack.is_empty() {
@@ -451,7 +461,7 @@ impl MachineState {
i += 1;
} else {
let tr = self.tr;
let val = self.trail[tr - 1];
let val = self.trail[tr - 1].clone();
self.trail[i] = val;
self.trail.pop();
self.tr -= 1;
@@ -474,11 +484,11 @@ impl MachineState {
match self.store(self.deref(addr)) {
Addr::HeapCell(hc) => {
self.heap[hc] = HeapCellValue::Addr(Addr::Con(c.clone()));
self.trail(Ref::HeapCell(hc));
self.trail(TrailRef::HeapCell(hc));
},
Addr::StackCell(fr, sc) => {
self.and_stack[fr][sc] = Addr::Con(c.clone());
self.trail(Ref::StackCell(fr, sc));
self.trail(TrailRef::StackCell(fr, sc));
},
Addr::Con(Constant::String(ref mut s)) =>
self.fail = match c {