This is related to the regex parser module. I'm trying to fix a problem encountered when trying to use multiple user-defined add-on modules.

The base class (for these purposes) for a "quant" object is Rx::quant. If you write an add-on, MyRxA, then a MyRxA::quant object's @ISA is (Rx::quant). If you write an add-on, MyRxB, then a MyRxB::quant object's @ISA is (Rx::quant).

MyRxA::quant::raw() changes the output of all quantifiers to '%' characters; this means a+b would render as a%b. 

package MyRxA::quant;
sub raw {
  my $self = shift;
  return "%";
}

[download]
MyRxB::quant::visual() makes the quantifier appear before the thing it quantifies; a+b would render as +ab. 
package MyRxB::quant::visual;
sub visual {
  my $self = shift;
  return $self->raw . $self->{data}->visual;
}

[download]

Now we want to write MyRxC, which uses MyRxA and MyRxB as base classes. This means we want a+b to render as %ab. (Confusing? Sorry. Just bear with me.) The problem is that, because of the way @ISA is set up, an object of MyRxC::quant has the following inheritence tree:

This means any call to a method of a MyRxC::quant object would only be re-dispatched to the MyRxA::quant namespace, and no method in MyRxB::quant would ever be called.

I haven't considered the more difficult scenario of two classes overriding the same method.

I'm stuck. I'm not sure how to traverse the @ISA tree properly. I don't think NEXT has the right tools for the job. I kind of want an "OVER::", not a "NEXT::" or "SUPER::". It looks like I want a breadth-first @ISA scan, not a depth-first scan. What I really want is to avoid looking in Rx for the method until the VERY end. Maybe the solution, then, is not to put Rx in the @ISA tree, but rather to look in Rx after all others have failed, via AUTOLOAD?

_____________________________________________________
Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;

In reply to Multiple Inheritence, Munging @ISA by japhy

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