From 79bb0008ec9afa8d8cee9e6b807a579bcb1c92ab Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <e.dolstra@tudelft.nl>
Date: Fri, 19 Mar 2004 14:45:45 +0000
Subject: [PATCH] * `null' is a normal form.

---
 src/libexpr/eval.cc | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 335f44baac..7ee157c316 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -186,14 +186,17 @@ Expr evalExpr2(EvalState & state, Expr e)
     ATerm name;
 
     /* Normal forms. */
-    if (atMatch(m, e) >> "Str" ||
-        atMatch(m, e) >> "Path" ||
-        atMatch(m, e) >> "Uri" ||
-        atMatch(m, e) >> "Int" ||
-        atMatch(m, e) >> "Bool" ||
-        atMatch(m, e) >> "Function" ||
-        atMatch(m, e) >> "Attrs" ||
-        atMatch(m, e) >> "List")
+    string cons;
+    if (atMatch(m, e) >> cons &&
+        (cons == "Str" ||
+         cons == "Path" ||
+         cons == "Uri" ||
+         cons == "Null" ||
+         cons == "Int" ||
+         cons == "Bool" ||
+         cons == "Function" ||
+         cons == "Attrs" ||
+         cons == "List"))
         return e;
 
     /* Any encountered variables must be undeclared or primops. */