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

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

Log Message:
-----------
BACKPORT: 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).

Tags:
----
rel-2-4-patches

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

Revision Data
-------------
Index: parserFormulaUpToConstant.pl
===================================================================
RCS file: /webwork/cvs/system/pg/macros/parserFormulaUpToConstant.pl,v
retrieving revision 1.11.2.1
retrieving revision 1.11.2.1.2.1
diff -Lmacros/parserFormulaUpToConstant.pl -Lmacros/parserFormulaUpToConstant.pl -u -r1.11.2.1 -r1.11.2.1.2.1
--- macros/parserFormulaUpToConstant.pl
+++ macros/parserFormulaUpToConstant.pl
@@ -175,9 +175,9 @@
   #
   #  Compare with adaptive parameters to see if $l + n0 C = $r for some n0.
   #
-  $main::_cmp_ = sub {return $l->{adapt} == $r};    # a closure to access local variables
-  my $equal = main::PG_restricted_eval('&$_cmp_');  # prevents errors with large adaptive parameters
-  delete $main::{_cmp_};                            # remove temprary function
+  $main::{_cmp_} = sub {return $l->{adapt} == $r};            # a closure to access local variables
+  my $equal = main::PG_restricted_eval('&{$main::{_cmp_}}');  # prevents errors with large adaptive parameters
+  delete $main::{_cmp_};                                      # remove temprary function
   return -1 unless $equal;
   #
   #  Check that n0 is non-zero (i.e., there is a multiple of C in the student answer)
@@ -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);
   }