Re^2: Functional Programming & method rewriting

About closures.

I don't generally use the hyper-technical definition that a closure is "anything that closes around a lexical", because that's true of any subroutine that is in a lexical environment.

I'm not sure how to interpret you, but it seems we view things differently. Either way a clarification probably would serve well. My definition of a closure in Perl is a subroutine that (deeply) binds a lexical variable. Whether it's called once or twice or a thousand times isn't relevant.

{ my $foo; sub foo { 1 } }      # not a closure
{ my $foo; sub foo { $foo } }   # a closure
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It's not about being "hyper-technical", it's about getting at the essence of what a closure is. That the bound variables doesn't go out of scope doesn't make it less of a closure, but its closureness doesn't get used. I understand that this is your point and I can almost sympathize with it, but just almost. It would be very confusing if a subroutine first wasn't a closure, but then became one when it was returned or assigned to variable with a broader scope.

Your point is supported by that we don't usually call &foo in

my $GLOBAL = 1;

sub foo {
    ... ; 
    ... $GLOBAL ... ;
    ... ;
}
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a closure. However, it is a closure and it's not wrong calling it one.

ihb

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Re^3: Functional Programming & method rewriting
by revdiablo (Prior) on Oct 30, 2004 at 22:11 UTC

First off, I want to thank you for actually engaging in a conversation, rather than simply writing me off as whiney and pedantic. I posted about something that I wanted to discuss, not just whine about. :-)

That it doesn't go out of scope doesn't make it less of a closure, but its closureness doesn't get used.

Indeed, that's true. I suppose I shouldn't try to fight against the technical definition. Rather than saying it's not a closure, I should have said it's not very useful to talk about its closure-ness.

However, it is a closure and it's not wrong calling it one.

Ok, fair enough. I officially change my position on the matter. Again, thank you for responding. I hope our friend SpanishInquisition is not too upset about the matter to read what I've written here, so he won't think I'm a completely horrible person.

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