bug fixes on LCO, backtracking.

2017-12-10 01:24:23 -07:00
parent e44ad111c5
commit 37f4450c34
9 changed files with 107 additions and 106 deletions
--- a/src/prolog/or_stack.rs
+++ b/src/prolog/or_stack.rs
@@ -78,10 +78,12 @@ impl OrStack {
        self.0.last()
    }

-    pub fn pop(&mut self) {
-        self.0.pop();
+    // truncate expects a 1-indexed new_b, ie.
+    // the value b of MachineState.
+    pub fn truncate(&mut self, new_b: usize) {
+        self.0.truncate(new_b);
    }
-
+    
    pub fn is_empty(&self) -> bool {
        self.0.is_empty()
    }