> Date: Thu, 09 Jan 2003 19:55:20 -0500
> From: John Siracusa <[EMAIL PROTECTED]>
>
> Has there been any discussion of how to create code in Perl 6 that's there
> under some conditions, but not there under others? I'm thinking of the
> spiritual equivalent of #ifdef, only Perlish.
>
> In Perl 5, there were many attempts to use such a feature for debugging and
> assertions. What everyone wanted to do was write code like this:
>
> debug("Doing foo with $bar and $baz");
> foo($bar, $baz);
> And then have the entire call to debug() just plain disappear when the
> program was run with a certain flag, or when a particular constant was set,
> or whatever. The closest we got in Perl 5, AFAIK, was stuff this:
>
> use constant DEBUG => 0;
> ...
> debug("Doing foo with $bar and $baz") if DEBUG;
> foo($bar, $baz);
Well, I just do:
sub debug {
print STDERR shift, "\n" if DEBUG;
}
And hopefully (I don't know P5 internals so well) that optimizes to a
no-op so there's not even a function call there. But it's a
negligible overhead anyway.
> But all those "if DEBUG"s or "DEBUG &&"s were a pain. So I'm wondering what
> the solution will be in Perl 6.
Not that C code is devoid of C<#ifdef>s everywhere there's conditional
code....
I don't see how you could do much without actually labeling what you
wanted to disappear. You could always use:
sub debug(&code) {
&code() if DEBUG;
}
For a more versatile and readable solution. I'm not sure what could
be more concise than that.
Luke
