From: Mark Thom <markjordanthom@gmail.com>
Date: Mon, 3 Sep 2018 06:20:01 +0000 (-0600)
Subject: do not unify partial strings unless they coincide in memory
X-Git-Tag: v0.8.110~403
X-Git-Url: https://git.sagredo.dev/?a=commitdiff_plain;h=3960ea4f06d0188a406e5b5aa253d85d86a7f9c4;p=scryer-prolog.git

do not unify partial strings unless they coincide in memory
---

diff --git a/src/prolog/machine/machine_state_impl.rs b/src/prolog/machine/machine_state_impl.rs
index 2e223b6e..87473934 100644
--- a/src/prolog/machine/machine_state_impl.rs
+++ b/src/prolog/machine/machine_state_impl.rs
@@ -254,7 +254,7 @@ impl MachineState {
 
                                         return true;
                                     }
-                                } else if s2.is_expandable() {                                
+                                } else if s2.is_expandable() {
                                     pdl.push(Addr::Con(Constant::String(s2.push_char(c1))));
                                     pdl.push(Addr::Con(Constant::String(s1.tail())));
 
@@ -264,12 +264,12 @@ impl MachineState {
                                 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() {
+                                } else if s2.is_expandable() {
+                                    return s1 == s2;
+                                } else {
                                     s1.set_non_expandable();
-                                }/*else {
-                                 //TODO: unify the tails of s1 and s2? I guess?
-                                }*/
-                                
+                                }
+
                                 return true;
                             } else if s2.head().is_none() {
                                 s2.set_non_expandable();
@@ -1445,7 +1445,7 @@ impl MachineState {
 
         false
     }
-    
+
     pub(super) fn compare_term_test(&self, a1: &Addr, a2: &Addr) -> Ordering {
         let iter = self.zipped_acyclic_pre_order_iter(a1.clone(), a2.clone());
 
@@ -1526,7 +1526,7 @@ impl MachineState {
                  HeapCellValue::Addr(Addr::Con(Constant::Number(_)))) =>
                     return Ordering::Greater,
                 (HeapCellValue::Addr(Addr::Con(Constant::String(s1))),
-                 HeapCellValue::Addr(Addr::Con(Constant::String(s2)))) =>                    
+                 HeapCellValue::Addr(Addr::Con(Constant::String(s2)))) =>
                     return s1.cmp(&s2),
                 (HeapCellValue::Addr(Addr::Con(Constant::String(_))), _) =>
                     return Ordering::Less,
diff --git a/src/tests.rs b/src/tests.rs
index f165c0ab..bc5b9289 100644
--- a/src/tests.rs
+++ b/src/tests.rs
@@ -1881,6 +1881,9 @@ fn test_queries_on_string_lists()
     assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X).",
                            [["X = [a, b, c | _]"]]);
 
+    assert_prolog_failure!(&mut wam, "?- partial_string(\"abc\", X), partial_string(\"abc\", Y), matcher(X, V),
+                                         matcher(Y, Z), V = Z.");
+
     submit(&mut wam, "matcher([a, b, c | X], X).");
 
     assert_prolog_success!(&mut wam, "?- partial_string(\"abc\", X), matcher(X, Y).",