--- rat/lonuserstate.pm	2006/04/27 23:36:10	1.108
+++ rat/lonuserstate.pm	2006/05/05 15:50:20	1.109
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # Construct and maintain state and binary representation of course for user
 #
-# $Id: lonuserstate.pm,v 1.108 2006/04/27 23:36:10 albertel Exp $
+# $Id: lonuserstate.pm,v 1.109 2006/05/05 15:50:20 albertel Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -413,16 +413,18 @@ sub accinit {
     foreach my $key (keys(%hash)) {
 	if ($key=~/^conditions/) {
 	    my $expr=$hash{$key};
+	    # try to find and factor out common sub-expressions
 	    foreach my $sub ($expr=~m/(\(\([_\.\d]+(?:\&[_\.\d]+)+\)(?:\|\([_\.\d]+(?:\&[_\.\d]+)+\))+\))/g) {
 		my $orig=$sub;
-		$sub=~/\(\(([_\.\d]+\&(:?[_\.\d]+\&)*)(?:[_\.\d]+\&*)+\)(?:\|\(\1(?:[_\.\d]+\&*)+\))+\)/;
-		my $factor=$1;
-		$sub=~s/$factor//g;
+
+		my ($factor) = ($sub=~/\(\(([_\.\d]+\&(:?[_\.\d]+\&)*)(?:[_\.\d]+\&*)+\)(?:\|\(\1(?:[_\.\d]+\&*)+\))+\)/);
+		next if (!defined($factor));
+
+		$sub=~s/\Q$factor\E//g;
 		$sub=~s/^\(/\($factor\(/;
 		$sub.=')';
 		$sub=simplify($sub);
-		$orig=~s/(\W)/\\$1/g;
-		$expr=~s/$orig/$sub/;
+		$expr=~s/\Q$orig\E/$sub/;
 	    }
 	    $hash{$key}=$expr;
 	    unless (defined($captured{$expr})) {