* Replaced the SDF parser by a substantially faster Bison/Flex

  parser (roughly 80x faster).

  The absolutely latest version of Bison (1.875c) is required for
  reentrant GLR support, as well as a recent version of Flex (say,
  2.5.31).  Note that most Unix distributions ship with the
  prehistoric Flex 2.5.4, which doesn't support reentrancy.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 0470deee9c0c..77cab55d034c 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -137,6 +137,8 @@ Expr evalExpr2(EvalState & state, Expr e)
     /* Any encountered variables must be undeclared or primops. */
     if (atMatch(m, e) >> "Var" >> s1) {
         if (s1 == "null") return primNull(state);
+        if (s1 == "true") return ATmake("Bool(True)");
+        if (s1 == "false") return ATmake("Bool(False)");
         return e;
     }