Re: Function Prototype Context Conversion

[chromatic]

Why can't @foo be treated as an implicit list for DWIM purposes?

Because that would make the following code terribly ambiguous:

my @foo = ( 1 .. 5 );
my $list-to-scalar  = @foo;
my $length-of-array = @foo;

[tadman]

No, that much is clearly understood. What I mean is that with respect to function prototypes, passing an array to a scalar prototype would seem to be a type mismatch, although these are kind of relative in such a loosely typed language as Perl. You'd hope for a warning, perhaps. You've asked for a scalar, but you're getting a list.

What I was expecting was that the @foo array would be expanded into the brackets in the function call and passed through as a list, but Perl appears to be doing some truly clever things to try and handle the prototype, taking it to the ultimate extreme.

Update:
japhy and everyone else who has been kind enough to post remarks on this subject is 100% correct, of course. What led to this insight into prototypes was one part ass, one part you, one part me, and we all know what that adds up to.

The counter-intuitive component of this is that I'd expected an automatic array-to-list conversion to be peformed before said list is then passed to the prototype, but this is not the case. A list of an array is not the same as a list of the array elements.

[japhy]

tadman: You've asked for a scalar, but you're getting a list.

Ah, not so! You've ask for a scalar, but you're getting an array! If you had done:

sub foo ($) { ... }

@a = (1,10,100);
foo(@a);        # no error, '3' is passed to foo()
foo(1,10,100);  # error, too many args

you'd have seen. Arrays and lists are not the same thing.

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Jeff[japhy]Pinyan: Perl, regex, and perl hacker, who'd like a job (NYC-area)
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