Re: [FWP] Self Aware Data routines?

[Ronald J Kimball <rjk@linguist.dartmouth.edu>]

On Mon, Jun 28, 1999 at 03:48:18PM -0400, Bill Jones wrote:
> >From: Ronald J Kimball <rjk@linguist.dartmouth.edu>
> 
> >> |sub AUTOLOAD { 
> >> |  print "Sorry, I don't see a subroutine called '$AUTOLOAD'\n";
> >> |}
> >>
> >> And hope that __DATA__ doesn't contain the name of some unrelated sub
> >> in main...
> >>
> >
> > That concern is valid for the general exercise, not just this specific
> > solution.  But under this exercise, there are no 'unrelated' subs.  The
> > idea is simply to call the specified sub if it exists, and print an
> > appropriate message if it doesn't.
> 
> (I am definitely a baby perl're :)
> 
> But would not using AUTOLOAD, which I had overlooked in my earlier post,
> allow one to look at other name spaces and call those subroutines if they
> exist?
> 

The same is true of your original code.

Actually, the difference between the original code, using defined(), and
this code, using &AUTOLOAD, is not in how they handle other package's
subroutines that do exist, but how they handle other package's
subroutines that don't exist.

With the original code, if you ask for Foo::Bar, and Foo::Bar does not
exist, then the code prints the "Sorry, I don't see a Subroutine Foo::Bar"
message.  But with the AUTOLOAD() code, in the same situation, then you get
the fatal error "Undefined subroutine &Bar::Foo called", because there is
no &Foo::AUTOLOAD.  (Or, if there is a &Foo::AUTOLOAD, then that will be
called instead of our &::AUTOLOAD.)

Ronald

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