* Models' SubstitutionMaps are now attached to the user context

  (rather than SAT context)
* Enable part of CVC3 system test (resolves bug 375)
* Fix infinite recursion in beta reduction code (resolves bug 417)
* Some model-building assertions have been added
* Other minor changes

(this commit was certified error- and warning-free by the test-and-commit script.)

1 files changed, 17 insertions, 1 deletions

diff --git a/src/theory/uf/theory_uf_rewriter.h b/src/theory/uf/theory_uf_rewriter.h
index f70d89b30..50211f1ad 100644
--- a/src/theory/uf/theory_uf_rewriter.h
+++ b/src/theory/uf/theory_uf_rewriter.h
@@ -77,7 +77,23 @@ public:
       for(TNode::iterator formal = lambda[0].begin(), arg = node.begin(); formal != lambda[0].end(); ++formal, ++arg) {
         // typechecking should ensure that the APPLY_UF is well-typed, correct arity, etc.
         Assert(formal != node.end());
-        substitutions.addSubstitution(*formal, *arg);
+        // This rewrite step is important: if we have (f (f 5)) for
+        // some lambda term f, we want to beta-reduce the inside (f 5)
+        // application first.  Otherwise, we can end up in infinite
+        // recursion, because f's formal (say "x") gives the
+        // substitution "x |-> (f 5)".  Fine, the body of the lambda
+        // gets (f 5) in place for x.  But since the same lambda ("f")
+        // now occurs in the body, it's got the same bound var "x", so
+        // substitution continues and we replace that x by (f 5).  And
+        // then again.  :-(
+        //
+        // We need a better solution for distinguishing bound
+        // variables like this, but for now, handle it by going
+        // inside-out.  (Quantifiers shouldn't ever have this problem,
+        // so long as the bound vars in different quantifiers are kept
+        // different.)
+        Node n = Rewriter::rewrite(*arg);
+        substitutions.addSubstitution(*formal, n);
       }
       return RewriteResponse(REWRITE_DONE, substitutions.apply(lambda[1]));
     }