[WWcvs] pg: Updated to be able to handle empty anwswer blanks.

[dpvc v. a. <we...@ma...>]

Log Message:
-----------
Updated to be able to handle empty anwswer blanks.  There is a new
parameter for the MultiPart object (allowBlankAnswers) that controls
whether the checker routine will be called even when there are blank
entries (normally, the checker is not called unless all the entries
are non-blank).  Use 

  $mp = MultiPart(1,2)->with(checkTypes=>0,allowBlankAnswers=>0);

to have the checker routine called when answers are left blank.

You can now also include blank answers in the list itself:

  $mp = MultiPart(1,2,"");

(there is no need to include allowBlankAnswers in this case, because
the blank string will take care of itself.

Modified Files:
--------------
    pg/macros:
        parserMultiPart.pl

Revision Data
-------------
Index: parserMultiPart.pl
===================================================================
RCS file: /webwork/cvs/system/pg/macros/parserMultiPart.pl,v
retrieving revision 1.3
retrieving revision 1.4
diff -Lmacros/parserMultiPart.pl -Lmacros/parserMultiPart.pl -u -r1.3 -r1.4
--- macros/parserMultiPart.pl
+++ macros/parserMultiPart.pl
@@ -29,7 +29,7 @@
 #  You need to provide a checker routine that will be called to determine if the
 #  answers are correct or not.  The checker will only be called if the student
 #  answers have no syntax errors and their types match the types of the professor's
-#  answers, so you don't ahve to worry about handling bad data from the student
+#  answers, so you don't have to worry about handling bad data from the student
 #  (at least as far as typechecking goes).
 #
 #  The checker routine should accept three parameters:  a reference to the array
@@ -103,7 +103,7 @@
 #                                 or one for each answer rule.
 #                                 (Default: 0)
 #
-#      namedRules => 0 or 1       wether to use named rules or default
+#      namedRules => 0 or 1       whether to use named rules or default
 #                                 rule names.  Use named rules if you need
 #                                 to intersperse other rules with the
 #                                 ones for the MultiPart, in which case
@@ -117,6 +117,12 @@
 #                                 the types before you use the data).
 #	                          (Default: 1)
 #
+#      allowBlankAnswers=>0 or 1  whether to remove the blank-check prefilter
+#                                 from the answer checkers for the answer
+#                                 checkers used for type checking the student's
+#                                 answers.
+#                                 (Default: 0)
+#
 #      separator => string        the string to use between entries in the
 #                                 results area when singleResult is set.
 #
@@ -139,7 +145,8 @@
   }
   bless {
     data => [@data], cmp => [@cmp], ans => [],
-    part => 0, singleResult => 0, namedRules => 0, checkTypes => 1,
+    part => 0, singleResult => 0, namedRules => 0,
+    checkTypes => 1, allowBlankAnswers => 0,
     tex_separator => $separator.'\,', separator => $separator.' ',
     context => $$Value::context, id => $answerPrefix.($count++),
   }, $class;
@@ -159,6 +166,17 @@
     }
   }
   die "You must supply a checker subroutine" unless ref($self->{checker}) eq 'CODE';
+  if ($self->{allowBlankAnswers}) {
+    foreach my $cmp (@{$self->{cmp}}) {
+      $cmp->install_pre_filter('erase');
+      $cmp->install_pre_filter(sub {
+	my $ans = shift;
+	$ans->{student_ans} =~ s/^\s+//g;
+	$ans->{student_ans} =~ s/\s+$//g;
+	return $ans;
+      });
+    }
+  }
   my @cmp = ();
   if ($self->{singleResult}) {
     push(@cmp,$self->ANS_NAME(0)) if $self->{namedRules};
@@ -278,7 +296,7 @@
   my $i = $ans->{part};
   $self->{ans}[$i] = $self->{cmp}[$i]->evaluate($ans->{student_ans});
   $self->{ans}[$i]->score(0);
-  $self->perform_check if ($i == $self->length - 1);
+  $self->perform_check($ans) if ($i == $self->length - 1);
   return $self->{ans}[$i];
 }
 
@@ -294,7 +312,8 @@
 #  Set the individual scores based on the result from the user's routine.
 #
 sub perform_check {
-  my $self = shift; $self->{context}->clearError;
+  my $self = shift; my $rh_ans = shift;
+  $self->{context}->clearError;
   my @correct; my @student;
   foreach my $ans (@{$self->{ans}}) {
     push(@correct,$ans->{correct_value});
@@ -302,7 +321,7 @@
     return if $ans->{ans_message} ne "" || !defined($ans->{student_value});
     return if $self->{checkTypes} && $ans->{student_value}->type ne $ans->{correct_value}->type;
   }
-  my $result = Value::cmp_compare([@correct],[@student],$self);
+  my $result = Value::cmp_compare([@correct],[@student],$self,$rh_ans);
   if (!defined($result) && $self->{context}{error}{flag}) {$self->cmp_error($self->{ans}[0]); return 1}
   $result = 0 if (!defined($result) || $result eq '');
   if (ref($result) eq 'ARRAY') {