wantarray like wanthash

slloyd has asked for the wisdom of the Perl Monks concerning the following question:

Is there a way to determine what the caller is wanting to return other than 'wantarray'? Can I determine if the list the caller wants is a hash?

use strict;

my $txt=callMe(1,2,3);
print "txt=$txt\n";
my @tmp=callMe(1,2,3);
print "tmp=@tmp\n";
my %list=callMe(1,2,3);
foreach my $key (keys(%list)){print "list{$key}=$list{$key}\n";}

sub callMe{
    my @in=@_;
    if(wantarray){
        #how do I determine if the caller wants an array or a hash?
        return reverse(@in);
        }
    else{return join(",",reverse(@in));}
    }
[download]

--------------------
txt=3,2,1
tmp=3 2 1
list{1}=
list{3}=2

-------------------------------
by me
http://www.basgetti.com
http://www.kidlins.com

Comment on wantarray like wanthash Download Code

Replies are listed 'Best First'.
Re: wantarray like wanthash by dragonchild (Archbishop) on Dec 12, 2005 at 21:03 UTC
"wantarray" is really a misnomer. It should be called "wantlist" because what it determines is if the calling context is list, scalar, or void. You're looking for Contextual::Return. My criteria for good software: Does it work? Can someone else come in, make a change, and be reasonably certain no bugs were introduced?	[reply]
Re: wantarray like wanthash by Roy Johnson (Monsignor) on Dec 12, 2005 at 21:02 UTC
Nothing built-in, because it's really just telling you whether the sub was called in scalar, list, or void context. Look at Want for a module that gives you more contexts. Caution: Contents may have been coded under pressure.	[reply]
Re: wantarray like wanthash by Fletch (Bishop) on Dec 12, 2005 at 21:03 UTC
If you do some searching you'll find discussion on how `wantarray` would have been more properly named `wantlist`. There's three contexts: scalar, list, and void. Assigning to a hash is just using the fact that a hash can be initialized from a list of key-value pairs (so no, you couldn't tell the difference).	[reply] [d/l] [select]
Re: wantarray like wanthash by GrandFather (Saint) on Dec 12, 2005 at 21:15 UTC
`wantarray` should perhps be called something like `callcontext`. For this purpose Perl has three contexts: void, scalar and list, and `wantarray` is `undef`, `false` and `true`. Note in general that in list context a hash turns into an array in any case - think for example what happens when you pass a hash into a sub. To that extent hashes and arrays are interchangeable. Consider this: `use warnings; use strict; use Data::Dumper; my %hash = (first => '1', second => '2'); print "Original: " . Dumper (\%hash); my %newHash = %{inAndOut (%hash)}; print "\nnew hash: " . Dumper (\%newHash); sub inAndOut { my (%hash) = @_; print "\nin sub: " . Dumper (\%hash); return {%hash}; }` [download] prints: `Original: $VAR1 = { 'first' => '1', 'second' => '2' }; in sub: $VAR1 = { 'first' => '1', 'second' => '2' }; new hash: $VAR1 = { 'first' => '1', 'second' => '2' };` [download] DWIM is Perl's answer to Gödel	[reply] [d/l] [select]
Re: wantarray like wanthash by jZed (Prior) on Dec 12, 2005 at 21:34 UTC
`#!/usr/bin/perl -w use strict; use Data::Dumper; my %hash = try_it(); my $scalar = try_it(); print Dumper \%hash; print "\n$scalar\n"; sub try_it { return (a=>1,b=>2) if wantarray; return "foo"; }` [download]	[reply] [d/l]