[Oc-pm] Meeting Notes

[Ben Tilly]

On 5/25/07, Mark D. Nagel <mnagel at willingminds.com> wrote:
> Ben Tilly wrote:
> > You can't really do the Y Combinator in Perl because one of the key
> > points of the combinator is that you should not need any form of
> > assignment, and Perl can't process function arguments without using
> > assignment.
>
> I'm not familiar with all the details on this one, but is the problem
> that when you use function arguments without assignment that they are
> passed by reference?  Because I know you can process arguments without
> assignment as long as they are not altered (unless that is the intent)
> and you don't mind line noise :).

Passed by reference is not the problem.  Dynamic scoping is.

To make the Y Combinator work you need to use currying, and currying
requires lexically scoped variables.  Currying is turning things like

  F = function (i, j) {
    ...
  };
  F(i,j);

into things like

  F = function (i) { return function (j) {
    ...
  }};
  F(i)(j);

but that only works if the anonymous function returned by the second
version of F actually has i lexically scoped.

Cheers,
Ben