Re: Re: Re: 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, $barref) = your_function();
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Re: Re: Re: Re: array or scalar, that's the question by Juerd (Abbot) on Jan 02, 2002 at 00:21 UTC
When you say "`return @bar`" Perl flattens `@bar` into a list. That's what happens in _list_ context. If the sub is called in scalar context, `@bar` will also be in scalar context and thus return the number of elements in `@bar`. `sub foo { my @foo = qw(a b c d); return @foo; } sub bar { return qw(15 4 3 12); } print foo(), "\n"; # list context => abcd\n print scalar foo(), "\n"; # scalar context => 4\n print bar(), "\n"; # list context => 154312\n print scalar bar(), "\n"; # scalar context => 12\n` [download] Explanation: a list returns its last element in scalar context, an array returns the number of elements in scalar context. `2;0 juerd@ouranos:~$ perl -e'undef christmas' Segmentation fault 2;139 juerd@ouranos:~$` [download]	[reply] [d/l] [select]
Re: Re: Re: Re: Re: array or scalar, that's the question by Fastolfe (Vicar) on Jan 03, 2002 at 00:01 UTC
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.	[reply]


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