--- loncom/homework/default_homework.lcpm	2005/03/28 19:20:54	1.95
+++ loncom/homework/default_homework.lcpm	2005/03/29 17:57:51	1.96
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA 
 # used by lonxml::xmlparse() as input variable $safeinit to Apache::run::run()
 #
-# $Id: default_homework.lcpm,v 1.95 2005/03/28 19:20:54 albertel Exp $
+# $Id: default_homework.lcpm,v 1.96 2005/03/29 17:57:51 albertel Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -529,13 +529,17 @@ sub format {
 
 sub chemparse {
     my ($reaction) = @_;
-    my @tokens = split(/(\s\+|\->|<=>)/,$reaction);
+    my @tokens = split(/(\s\+|\->|<=>|<\-|\.)/,$reaction);
     my $formula = '';
     foreach my $token (@tokens) {
 	if ($token eq '->' ) {
 	    $formula .= '<m>\ensuremath{\rightarrow}</m> ';
 	    next;
 	}
+	if ($token eq '<-' ) {
+	    $formula .= '<m>\ensuremath{\leftarrow}</m> ';
+	    next;
+	}  
 	if ($token eq '<=>') {
 	    if ($external::target eq 'web' &&
 		&EXT('request.browser.unicode')) {
@@ -546,7 +550,12 @@ sub chemparse {
 	    }
 	    next;
 	}
-	$token =~ /^\s*(\d*(?:&frac\d\d)?)(.*)/;
+	if ($token eq '.') {
+	  $formula =~ s/(\&nbsp\;| )$//;
+	  $formula .= '&middot;';
+	  next;
+	}
+	$token =~ /^\s*([\d|\/]*(?:&frac\d\d)?)(.*)/;
         $formula .= $1 if ($1 ne '1');  # stoichiometric coefficient
 	
 	my $molecule = $2;
@@ -558,6 +567,7 @@ sub chemparse {
 	$molecule =~ s/\s*//g;
 	# forced space
 	$molecule =~ s/_/ /g;
+	$molecule =~ s/-/&minus;/g;
 	$formula .= $molecule.'&nbsp;';
     }
     # get rid of trailing space