[WWcvs] pg: Trap errors when comparing to student answer while trying to determine the correct error message.

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

Log Message:
-----------
Trap errors when comparing to student answer while trying to determine
the correct error message.  This prevents extraneous warnings that
would confuse the student (and instructor).

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

Revision Data
-------------
Index: parserFormulaUpToConstant.pl
===================================================================
RCS file: /webwork/cvs/system/pg/macros/parserFormulaUpToConstant.pl,v
retrieving revision 1.13
retrieving revision 1.14
diff -Lmacros/parserFormulaUpToConstant.pl -Lmacros/parserFormulaUpToConstant.pl -u -r1.13 -r1.14
--- macros/parserFormulaUpToConstant.pl
+++ macros/parserFormulaUpToConstant.pl
@@ -214,7 +214,10 @@
     my $context = $self->context;
     $context->flags->set(no_parameters=>0);
     $context->variables->add(x00=>'Real');
-    $result = 1 if $self->removeConstant+"n01+n00x00" == $student+"x00"; # must use both parameters
+    my $correct = $self->removeConstant+"n01+n00x00";    # must use both parameters
+    $main::{_cmp_} = sub {return $correct == $student+"x00"};     # a closure to access local variables
+    $result = 1 if main::PG_restricted_eval('&{$main::{_cmp_}}'); # prevents domain errors (and other errors)
+    delete $main::{_cmp_};                                        # remove temprary function
     $context->variables->remove('x00');
     $context->flags->set(no_parameters=>1);
   }