Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!caesar.cs.montana.edu!ogicse!hakanson
From: hakanson@ogicse.ogc.edu (Marion Hakanson)
Newsgroups: comp.lang.perl
Subject: Re: Subroutines Returning Null Arrays
Message-ID: <6712@ogicse.ogc.edu>
Date: 18 Jan 90 18:11:26 GMT
References: <13395@cit-vax.Caltech.Edu>
Reply-To: hakanson@ogicse.UUCP (Marion Hakanson)
Organization: Oregon Graduate Institute (formerly OGC), Beaverton, OR
Lines: 48

In article <13395@cit-vax.Caltech.Edu> joe@cit-750.cs.caltech.edu (Joe Beckenbach) writes:
>
>	Is there a way to force a subroutine to return a null array?

Now that you mention it, I've been wondering about some odd behavior
related to that for awhile.  I have a workaround, and I forgot to track
it down further.  Here's the workaround:

while ( (@a = do subr()) && @a ) {
    # fiddle with @a
}

Now I just tracked it down further.  Here's a test program which
demonstrates the problem (perl 3.0, pl6, anyway -- I didn't notice
a patch in 7&8):

==========cut here===========
#!/usr/bin/perl

sub nsub1
{
  ();
}

sub nsub2
{
  return ();
}


@nr1 = do nsub1();
print "nr1 has $#nr1 elements.\n";

@nr2 = do nsub2();
print "nr2 has $#nr2 elements.\n";
==========cut here===========

Here's the output:

nr1 has -1 elements.
nr2 has 0 elements.

It turns out that $nr2[0] is empty, which is why my "workaround"
works.  Definitely looks like a bug to me, though.  Larry?

-- 
Marion Hakanson         Domain: hakanson@cse.ogi.edu
                        UUCP  : {hp-pcd,tektronix}!ogicse!hakanson