--- loncom/homework/default_homework.lcpm	2011/06/09 15:43:56	1.159
+++ loncom/homework/default_homework.lcpm	2014/06/25 10:48:39	1.167
@@ -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 1.159 2011/06/09 15:43:56 www Exp $
+# $Id: default_homework.lcpm,v 1.167 2014/06/25 10:48:39 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -318,11 +318,13 @@ sub caparesponse_check_list {
 	    $responses->[0][-1]=$part1;
 	    $unit=&capa_formula_fix($part2);
             my $customunits=$LONCAPA::CAPAresponse_args{'customunits'};
-            foreach my $replacement (split(/\s*\,\s*/,$customunits)) {
-                my ($which,$what)=split(/\s*\=\s*/,$replacement);
-                if ((defined($which)) && (defined($what))) {
-                   $what=&capa_formula_fix($what);
-                   $unit=~s/$which/\($what\)/g;
+            if ($customunits =~ /\S/) {
+                foreach my $replacement (split(/\s*\,\s*/,$customunits)) {
+                    my ($which,$what)=split(/\s*\=\s*/,$replacement);
+                    if ((defined($which)) && (defined($what))) {
+                        $what=&capa_formula_fix($what);
+                        $unit=~s/$which/\($what\)/g;
+                    }
                 }
             }
 	}
@@ -357,7 +359,7 @@ sub caparesponse_check_list {
              $appendunit='%'.$appendunit;
           }
 # Zero does not need a dimension
-          if (($element==0) && ($unit!~/\w/) && ($answerunit=~/\w/)) {
+          if (($element =~ /^[0\.]+$/) && ($unit!~/\w/) && ($answerunit=~/\w/)) {
              $appendunit=$answerunit;
           }
 # Do the math for the student if allowed
@@ -814,6 +816,7 @@ sub cos { CORE::cos(shift) }
 sub exp { CORE::exp(shift) }
 sub int { CORE::int(shift) }
 sub log { CORE::log(shift) }
+sub ln { CORE::log(shift) }
 sub atan2 { CORE::atan2($_[0],$_[1]) }
 sub sqrt { CORE::sqrt(shift) }
 
@@ -1040,16 +1043,47 @@ sub format_significant_figures {
     my ($zeros) = ($xint =~ /(0+)$/);
     # return number to original magnitude
     my $numSig = $xint*10**($x10-$sig+$power);
-    # insert trailing zero's if have decimal point
-    $numSig =~ s/^(\d+)\.(\d+)(\e?(.*)?)$/$1\.$2$zeros$3/;
-    # put a decimal pt for number ending with 0 and length = # of sig fig
-    $numSig.='.' if (length($numSig) == $sig && $numSig =~ /0$/);
-    if (length($numSig) < $sig) {
-	$numSig.='.'.substr($zeros,0,($sig-length($numSig)));
+    if ($numSig =~ /^(\d+)\.(\d+)/) {
+        # insert trailing zero's if have decimal point
+        my @digarray = split('',$1.$2);
+        my $sigcount;
+        while (@digarray > 0) {
+            my $item = shift(@digarray);
+            if ($item) {
+                $sigcount = 1 + @digarray;
+                last;
+            }
+        }
+        if (($sigcount) && ($sig >= $sigcount)) {
+            $zeros = substr($zeros,0,($sig - $sigcount));
+        }
+        $numSig =~ s/^(\d+)\.(\d+)(\e?(.*)?)$/$1\.$2$zeros$3/;
+    } else {
+        if ($numSig =~ /^(\d+)e([\+\-]\d+)$/i) {
+            my $pre_exp = $1;
+            my $exponent = $2;
+            $numSig = $pre_exp.'.'.$zeros.'E'.$exponent;
+        } elsif ($numSig =~ /0$/) {
+            # add decimal pt for number ending with 0 and length == # of sig figs
+            if (length($numSig) == $sig) {
+                $numSig.='.';
+            } elsif (length($numSig) > $sig) {
+                # exponential form for number ending with 0 and length > # of sig figs
+                my $fmtsig = $sig-1;
+                if ($fmtsig) {
+                    $numSig = sprintf('%.'.$fmtsig.'E',$numSig);
+                }
+            } elsif (length($numSig) < $sig) {
+                $numSig.='.'.substr($zeros,0,($sig-length($numSig)));
+            }
+        } else {
+            if (length($numSig) < $sig) {
+                $numSig.='.'.substr($zeros,0,($sig-length($numSig)));
+            }
+        }
     }
     # return number with sign
     return $sign.$numSig;
-
 }
 
 sub map {
@@ -1181,7 +1215,6 @@ sub middlename {
     return $middlename;
 }
 
-                                                                                
 sub lastname {
     my $lastname = &EXT('environment.lastname');
     $lastname = '' if $lastname eq "";
@@ -1195,10 +1228,18 @@ sub sec {
 }
 
 sub submission {
-   my ($partid,$responseid,$subnumber)=@_;
+   my ($partid,$responseid,$subnumber,$encode)=@_;
    my $sub='';
    if ($subnumber) { $sub=$subnumber.':'; }
-   return &EXT('user.resource.'.$sub.'resource.'.$partid.'.'.$responseid.'.submission');
+   my $output =
+       &EXT('user.resource.'.$sub.'resource.'.$partid.'.'.$responseid.'.submission');
+   if ($encode) {
+       $output =~ s/&/&amp;/g;
+       $output =~ s/</&lt;/g;
+       $output =~ s/>/&gt;/g;
+       $output =~ s/"/&quot;/g;
+   }
+   return $output;
 }
 
 sub currentpart {