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Re: Re: Re: Reference to a sub return / Config::General

by revdiablo (Prior)
on Jan 22, 2004 at 22:58 UTC ( #323355=note: print w/replies, xml ) Need Help??


in reply to Re: Re: Reference to a sub return / Config::General
in thread Reference to a sub return / Config::General

But I thought maybe there was some way around it

If the subroutine returns a list instead of a hashref, there's not much you can do about it.

Just for a little bit more explanation: when you say return %hash, the hash gets flattened into a plain ol' list. When you subsequently say my %hash = foo(), that shoehorns the list into a new hash. Again, there's nothing you can do about this without modifying the subroutine's return statement.

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Re: Re: Re: Re: Reference to a sub return / Config::General
by Oberon (Monk) on Jan 23, 2004 at 16:05 UTC
    > when you say return %hash, the hash gets flattened into a plain ol' list. When you subsequently say my %hash = foo(), that shoehorns the list into a new hash.

    Ah, I hadn't thought of it that way. So I'm not only running into the difference between a value and a variable, but also the difference between a list and an array.

    Although, come to think of it, those are basically analogous ...

      So I'm not only running into the difference between a value and a variable, but also the difference between a list and an array.

      Right. The only way you can really return an array itself (or, as previously discussed, a hash) is with a reference. Just like with return %hash, when you write return @array, the array is flattened. The elements are sucked out and put into a list. The list is returned. The caller can then grab that list and do what it wants with it; be it iterate through it, suck it into a new array, or even suck it into a hash.

      It may seem complex at first, but really it's very simple. Your data structures get dismantled unless you use references.

      Before you dismay at what happens to multi-level datastructures, keep in mind that these are only achievable in Perl via the use of references. They're perfectly safe, so things like @array = ([qw/one two/], [qw/three four/]); return @array will not blow up into tiny pieces. 8^)

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