[WWcvs] pg: Changes to code checking whether the previous answer is equivalent

[Mike G. v. a. <we...@ma...>]

Log Message:
-----------

Changes to code checking whether the previous answer is equivalent to the current answer.
In this module additional code was answer to check for errors in the overloaded ==
in case the two Values can't be compared.

In PGanswermacros.pl the filter which handles "parse_previous_answer" 
was modified to make sure the context is the same in the previous answer and the current answer.

Modified Files:
--------------
    pg/lib/Value:
        AnswerChecker.pm
    pg/macros:
        PGanswermacros.pl

Revision Data
-------------
Index: AnswerChecker.pm
===================================================================
RCS file: /webwork/cvs/system/pg/lib/Value/AnswerChecker.pm,v
retrieving revision 1.71
retrieving revision 1.72
diff -Llib/Value/AnswerChecker.pm -Llib/Value/AnswerChecker.pm -u -r1.71 -r1.72
--- lib/Value/AnswerChecker.pm
+++ lib/Value/AnswerChecker.pm
@@ -204,14 +204,19 @@
 
 sub cmp_compare {
   my $self = shift; my $other = shift; my $ans = shift; my $nth = shift || '';
-  return eval {$self == $other} unless ref($ans->{checker}) eq 'CODE';
-  my $equal = eval {&{$ans->{checker}}($self,$other,$ans,$nth,@_)};
-  if (!defined($equal) && $@ ne '' && (!$$Value::context->{error}{flag} || $ans->{showAllErrors})) {
-    $$Value::context->setError(["<I>An error occurred while checking your$nth answer:</I>\n".
-      '<DIV STYLE="margin-left:1em">%s</DIV>',$@],'',undef,undef,$CMP_ERROR);
-    warn "Please inform your instructor that an error occurred while checking your answer";
+  my $equal = undef;
+  unless ( ref($ans->{checker}) eq 'CODE' ) {
+  	$equal = eval {$self == $other} ;
+  } else {
+	$equal = eval {&{$ans->{checker}}($self,$other,$ans,$nth,@_)};
+  }
+  if (!defined($equal) && $@ ne '' && ($$Value::context->{error}{flag} || $ans->{showAllErrors})) {
+	 $$Value::context->setError(["<I>An error occurred while checking your$nth answer:</I>\n".
+		  '<DIV STYLE="margin-left:1em">%s</DIV>',$@],'',undef,undef,$CMP_ERROR);
+	 warn "Please inform your instructor that an error occurred while checking your answer";
   }
   return $equal;
+
 }
 
 sub cmp_list_compare {Value::List::cmp_list_compare(@_)}
Index: PGanswermacros.pl
===================================================================
RCS file: /webwork/cvs/system/pg/macros/PGanswermacros.pl,v
retrieving revision 1.41
retrieving revision 1.42
diff -Lmacros/PGanswermacros.pl -Lmacros/PGanswermacros.pl -u -r1.41 -r1.42
--- macros/PGanswermacros.pl
+++ macros/PGanswermacros.pl
@@ -2006,7 +2006,9 @@
 	    my $rh_ans = shift;
 	    $rh_ans->{_filter_name} = "parse_previous_answer";
 	    return $rh_ans unless defined $rh_ans->{prev_ans};
+	    my $oldContext = &$Context(); &$Context($context);
 	    $rh_ans->{prev_formula} = Parser::Formula($rh_ans->{prev_ans});
+	    &$Context($oldContext);
 	    $rh_ans;
 	  }
 	);
@@ -2034,7 +2036,9 @@
 	    my $rh_ans = shift;
 	    $rh_ans->{_filter_name} = "produce_equivalence_message";
 	    return $rh_ans unless $rh_ans->{prev_equals_current} && $rh_ans->{score} == 0;
-	    return $rh_ans if $rh_ans->{prev_ans} eq $rh_ans->{original_student_ans};
+	    # the match is exact don't give an error since the previous entry
+	    # might have been from the preview button
+		return $rh_ans if $rh_ans->{prev_ans} eq $rh_ans->{original_student_ans};
 	    $rh_ans->{ans_message} = "This answer is equivalent to the one you just submitted or previewed.";
 	    $rh_ans;
 	  }