* In environments, store pointers to values rather than values. This

improves GC effectiveness a bit more (because a live value doesn't
  keep other values in the environment plus the parent environments
  alive), and removes the need for copy nodes.

src/libexpr/eval.hh

@@ -38,7 +38,6 @@ typedef enum {
     tThunk,
     tApp,
     tLambda,
-    tCopy,
     tBlackhole,
     tPrimOp,
     tPrimOpApp,
@@ -116,7 +115,7 @@ struct Env
 {
     Env * up;
     unsigned int prevWith; // nr of levels up to next `with' environment
-    Value values[0];
+    Value * values[0];
 };
 
 
@@ -150,13 +149,6 @@ static inline void mkThunk(Value & v, Env & env, Expr * expr)
 }
 
 
-static inline void mkCopy(Value & v, Value & src)
-{
-    v.type = tCopy;
-    v.val = &src;
-}
-
-
 static inline void mkApp(Value & v, Value & left, Value & right)
 {
     v.type = tApp;