Subj : Re: anyone know of a language where nonexistent functions return no error?
To   : comp.programming
From : gswork
Date : Fri Jul 22 2005 10:23 am



Jonathan Bartlett wrote:
> pantagruel wrote:
> >  An existent function calling such a nonexistent function would
> > basically be left with an empty string, unless the programmer defined
> > specific error generation. Theoretical literature welcome. hope this is
> > a reasonable question to ask here
> >
>
> Perl can do this and more (it can actually dynamically generate the
> given function at runtime).  If you define AUTOLOAD, it will be called
> for non-existant functions in the current package.  So if you have a
> program like this:
>
> sub AUTOLOAD
> {
> 	return "";
> }
>
> $test = foo();
>
> This does what you want.  Even better, you can have stuff like this
> (adapted from the Perl documentation):
>
> sub AUTOLOAD
> {
> 	my $name = our $AUTOLOAD;
> 	*$AUTOLOAD = sub { return "You were calling $name\n"; }
> 	goto &$AUTOLOAD;
> }
>
> $a = foo(); #$a now has "You were calling foo\n"
> $b = eee(); #$b now has "You were calling eee\n"
> $c = foo(); #same as above, but now that foo() is loaded, it doesn't
> call autoload any more

the question that came to my mind was "yes, interesting, but how is it
useful?"

It potentially creates the misspelled function problem (instead of
falling down it just accepts and masks the misspelling creating
potentially subtle bugs)

If using it as a throwaway function to fill out a rough framework for
an app then the same could be achieved by using a generic stub
function, e.g.

stub() { return "stub"; }

Only works in weakly typed langauges, though the perl idea could be
applied to a strongly typed language and made to return something
apropriate, e.g. int a=eee() returns the integer 0, string a=eee()
returns ""

I suppose it might be handy to create a function name that seems
appropriate and then go create the proper function later on, but in any
complex project that will lead to bugs, things being forgotten etc, and
a bunch of well named stub functions woulod do anyway.

So i'm intrigued now - what do folks use the feature for?

.