* After parsing, compute level/displacement pairs for each variable

use site, allowing environments to be stores as vectors of values
  rather than maps.  This should speed up evaluation and reduce the
  number of allocations.

src/libexpr/primops.cc

@@ -999,9 +999,11 @@ void EvalState::createBaseEnv()
 {
     baseEnv.up = 0;
 
+#if 0    
     Value & builtins = baseEnv.bindings[symbols.create("builtins")];
     builtins.type = tAttrs;
     builtins.attrs = new Bindings;
+#endif
 
     /* Add global constants such as `true' to the base environment. */
     Value v;
@@ -1023,9 +1025,11 @@ void EvalState::createBaseEnv()
 
     /* Add a wrapper around the derivation primop that computes the
        `drvPath' and `outPath' attributes lazily. */
+#if 0
     string s = "attrs: let res = derivationStrict attrs; in attrs // { drvPath = res.drvPath; outPath = res.outPath; type = \"derivation\"; }";
     mkThunk(v, baseEnv, parseExprFromString(*this, s, "/"));
     addConstant("derivation", v);
+#endif
 
     // Miscellaneous
     addPrimOp("import", 1, prim_import);