--- loncom/homework/chemresponse.pm	2004/06/07 21:17:42	1.33
+++ loncom/homework/chemresponse.pm	2004/06/07 21:56:24	1.34
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # chemical equation style response
 #
-# $Id: chemresponse.pm,v 1.33 2004/06/07 21:17:42 albertel Exp $
+# $Id: chemresponse.pm,v 1.34 2004/06/07 21:56:24 albertel Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -35,6 +35,33 @@ BEGIN {
     &Apache::lonxml::register('Apache::chemresponse',('organicresponse','organicstructure','reactionresponse'));
 }
 
+sub chem_standard_order {
+    my ($reaction) = @_;
+    my ($re,$pr) = split(/->|<=>/,$reaction);
+    my @reactants = split(/\s\+/,$re);
+    my @products =  split(/\s\+/,$pr);
+    foreach my $substance (@reactants,@products) {
+	$substance =~ s/(\^\d*)\s+/$1_/g;         # protect superscript space
+	$substance =~ s/\s*//g;                   # strip whitespace
+	$substance =~ s/_/ /g;                    # restore superscript space
+    }
+    @reactants = sort @reactants;
+    @products = sort @products;
+    my $standard = '';
+    foreach my $substance (@reactants) {
+	$standard .= $substance;
+	$standard .= ' + ';
+    }
+    $standard =~ s/ \+ $//;              # get rid of trailing plus sign
+    $standard .= ' -> ';
+    foreach my $substance (@products) {
+	$standard .= $substance;
+	$standard .= ' + ';
+    }
+    $standard =~ s/ \+ $//;              # get rid of trailing plus sign
+    return $standard;
+}
+
 sub separate_jme_window {
     my ($smile_input,$jme_input,$molecule,$options)=@_;
     my $smilesection;
@@ -345,7 +372,8 @@ sub end_reactionresponse {
 	    my $ad;
 	    foreach my $answer (@answers) {
 		&Apache::lonxml::debug("submitted a $response for $answer<br \>\n");
-		if ($response eq $answer) {
+		if (&chem_standard_order($response) eq 
+		    &chem_standard_order($answer)) {
 		    $ad='EXACT_ANS';
 		} else {
 		    $ad='INCORRECT';