in reply to Re: Re: array or scalar, that's the question
in thread array or scalar, that's the question

Differentiating between a "scalar" and an "array" is meaningless here. When you say "return @bar" Perl flattens @bar into a list. 
$foo = 3;
@bar = (1, 2, 3);

return $foo;       # (3)
return @bar;       # (1, 2, 3)

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In a scalar context, both of these versions will return 3 (the last element in the list returned). In a list context, you get 3 or 1, 2, 3. Just returning @bar, though, is sufficient for both cases, because it's your calling code that would want to act on the results. Make sense?

If you're wanting to return a real solid array (so that you can return @foo, @bar without flattening it into one big list), you need to return references to each array.

return (\@foo, \@bar);
...

my ($fooref, $barref) = your_function();

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Re: Re: Re: Re: array or scalar, that's the question
by Juerd (Abbot) on Jan 02, 2002 at 00:21 UTC
    When you say "return @bar" Perl flattens @bar into a list.
    That's what happens in _list_ context. If the sub is called in scalar context, @bar will also be in scalar context and thus return the number of elements in @bar.

    sub foo {
    my @foo = qw(a b c d);
    return @foo;
}
sub bar {
    return qw(15 4 3 12);
}

print        foo(), "\n"; #   list context => abcd\n
print scalar foo(), "\n"; # scalar context => 4\n
print        bar(), "\n"; #   list context => 154312\n
print scalar bar(), "\n"; # scalar context => 12\n

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    Explanation: a list returns its last element in scalar context, an array returns the number of elements in scalar context.

    2;0 juerd@ouranos:~$ perl -e'undef christmas'
Segmentation fault
2;139 juerd@ouranos:~$

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      You're right, I was being a bone-head. The '3' my examples returned wasn't the 3rd element, it was the fact that there were 3 elements in the array.

      So yes, there is a very important distinction, but if anything, it's another case for not differentiating between a "scalar" and an "array" in the function, because with one element, a scalar context returns that one element, whereas multiple elements will get returned as an array, causing a scalar context to return the number of items in that array. This change in behavior is probably undesirable.

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