[WWcvs] pg: Updated the answer checkers so that you can more easily specify how

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

Log Message:
-----------
Updated the answer checkers so that you can more easily specify how
the correct answer shoudl be displayed.  In the past, you could use
something like Real(sqrt(2))->cmp(correct_ans=>"sqrt(2)") to do this,
but that is awkward.  Now the Compute() function (which parses and
then evaluates a string) sets things up so that the original string
will be what is used as the correct answer.  That means
Compute("sqrt(2)")->cmp will have the same result as the example
above.

You can also set the {correct_ans} properly of any Parser object to
have that value used as the correct answer.  For example

     $x = Real(sqrt(2));
     $x->{correct_ans} = "sqrt(2)";
     ANS($x->cmp)

would also produce the same answer checker as the two previous
examples.  All three methods should work.  Use the one that is most
convenient for you.

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

Revision Data
-------------
Index: Parser.pl
===================================================================
RCS file: /webwork/cvs/system/pg/macros/Parser.pl,v
retrieving revision 1.4
retrieving revision 1.5
diff -Lmacros/Parser.pl -Lmacros/Parser.pl -u -r1.4 -r1.5
--- macros/Parser.pl
+++ macros/Parser.pl
@@ -30,8 +30,10 @@
 #  Parse a formula and evaluate it
 #
 sub Compute {
-  my $formula = Formula(shift);
-  return $formula->eval(@_);
+  my $string = shift;
+  my $formula = Formula($string)->eval(@_);
+  $formula->{correct_ans} = $string;
+  return $formula;
 }  
 
 #
Index: AnswerChecker.pm
===================================================================
RCS file: /webwork/cvs/system/pg/lib/Value/AnswerChecker.pm,v
retrieving revision 1.38
retrieving revision 1.39
diff -Llib/Value/AnswerChecker.pm -Llib/Value/AnswerChecker.pm -u -r1.38 -r1.39
--- lib/Value/AnswerChecker.pm
+++ lib/Value/AnswerChecker.pm
@@ -26,9 +26,11 @@
 sub cmp {
   my $self = shift;
   my $ans = new AnswerEvaluator;
+  my $correct = $self->{correct_ans};
+  $correct = $self->string unless defined($correct);
   $ans->ans_hash(
     type => "Value (".$self->class.")",
-    correct_ans => protectHTML($self->string),
+    correct_ans => protectHTML($correct),
     correct_value => $self,
     $self->cmp_defaults,
     @_
@@ -489,7 +491,8 @@
   my $cmp = $self->SUPER::cmp(@_);
   if ($cmp->{rh_ans}{removeParens}) {
     $self->{open} = $self->{close} = '';
-    $cmp->ans_hash(correct_ans => $self->stringify);
+    $cmp->ans_hash(correct_ans => $self->stringify)
+      unless defined($self->{correct_ans});
   }
   return $cmp;
 }
@@ -703,7 +706,8 @@
   my $cmp = $self->SUPER::cmp(@_);
   if ($cmp->{rh_ans}{removeParens} && $self->type eq 'List') {
     $self->{tree}{open} = $self->{tree}{close} = '';
-    $cmp->ans_hash(correct_ans => $self->stringify);
+    $cmp->ans_hash(correct_ans => $self->stringify)
+      unless defined($self->{correct_ans});
   }
   if ($cmp->{rh_ans}{eval} && $self->isConstant) {
     $cmp->ans_hash(correct_value => $self->eval);