[WWcvs] pg: Handle formula 'constants' properly

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

Log Message:
-----------
Handle formula 'constants' properly

Modified Files:
--------------
    pg/lib/Parser:
        Differentiation.pm

Revision Data
-------------
Index: Differentiation.pm
===================================================================
RCS file: /webwork/cvs/system/pg/lib/Parser/Differentiation.pm,v
retrieving revision 1.15
retrieving revision 1.16
diff -Llib/Parser/Differentiation.pm -Llib/Parser/Differentiation.pm -u -r1.15 -r1.16
--- lib/Parser/Differentiation.pm
+++ lib/Parser/Differentiation.pm
@@ -628,7 +628,8 @@
 #########################################################################
 
 sub Parser::Constant::D {
-  my $self = shift;
+  my $self = shift; my $x = shift;
+  return $self->{def}{value}{tree}->D($x) if Value::isFormula($self->{def}{value});
   $self->Item("Number")->new($self->{equation},0);
 }