* "!isNull x" -> "x != null". Done automatically. Hope nothing

broke.

svn path=/nixpkgs/trunk/; revision=870

pkgs/development/tools/parsing/bison/bison-new.nix

@@ -1,6 +1,6 @@
 {stdenv, fetchurl, m4}:
 
-assert !isNull m4;
+assert m4 != null;
 
 derivation {
   name = "bison-1.875c";

pkgs/development/tools/parsing/bison/default.nix

@@ -1,5 +1,5 @@
 {stdenv, fetchurl, m4}:
-assert !isNull m4;
+assert m4 != null;
 derivation {
   name = "bison-1.875";
   system = stdenv.system;

pkgs/development/tools/parsing/flex/default.nix

@@ -1,5 +1,5 @@
 {stdenv, fetchurl, yacc}:
-assert !isNull yacc;
+assert yacc != null;
 derivation {
   name = "flex-2.5.4a";
   system = stdenv.system;

pkgs/development/tools/parsing/flex/flex-new.nix

@@ -3,7 +3,7 @@
 
 {stdenv, fetchurl, yacc, m4}:
 
-assert !isNull yacc;
+assert yacc != null;
 
 derivation {
   name = "flex-2.5.31";