This is nothing more than a stroll down "what-if" lane. Earlier today I wondered to myself, what happens if I tie a scalar to a class whos FETCH() method attempts to return a list?

You usually hear the other side of the story: "There is no such thing as a list in scalar context." Well, this is just a different twist on the same concept, and with similar outcome. Not really of any use, but I found it thought-provoking.

For a brief moment I even thought it might be possible. But it appears that the scalar's own type provides some notion of context to the class to which it is tied, preventing a tied scalar from returning anything more than a scalar value.

Here's the example code... 

package ReturnList;

use strict;
use warnings;

sub TIESCALAR {
    my ( $class ) = @_; 
    my $self = {};
    $self->{Value} = undef;
    bless $self, $class; 
}

sub STORE { 
    my ( $self, $value ) = @_;
    push @{$self->{Value}}, $value;
    return $value;
}

sub FETCH { 
    my $self = shift;
    print "List context\n" if wantarray();
    return @{$self->{Value}};
}

1;

# ---------- Begin main ----------
package main;

use strict;
use warnings;

my $var;

tie $var, "ReturnList";

$var = 10;
$var = 20;
$var = 40;

my @array = $var;

print @array, "\n";

__OUTPUT__
3

[download]

'3' is the number of elements in the list. This shows that not only is it impossible for a scalar to be anything more than a scalar (even when tied), the very FETCH() method believes its being invoked in scalar context, even if we're trying to assign to an array.

I guess there really isn't a point to this post. But it seemed interesting to me. Anyone else?


Dave

In reply to If it looks like a scalar, and quacks like an array, it's still a scalar. by davido

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