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Re: return !!

by webfiend (Vicar)
on Mar 04, 2009 at 21:23 UTC ( [id://748325] : note . print w/replies, xml ) Need Help??

in reply to return !!

It's doing a couple things, although only one of them is relevant to the execution of code:

  • As mentioned, it's returning 1 if there are any items in @value, and false otherwise.
  • It's wreaking havoc on Vim's syntax highlighting.
  • It's wreaking havoc on my own poor brain trying to parse "not not (scalar) @value".

I'd probably use a more explicit test, as the following example shows (lexical variables added for my own peace of mind):

use Modern::Perl; sub mean_test { my @value = @_; return !!@value; } sub nicer_test { my @values = @_; return scalar @values > 0; } say "Mean: Empty: ", mean_test(); say "Mean: One Item: ", mean_test("sweet!"); say "Mean: Two Items: ", mean_test("dude!", "sweet!"); say "Nicer: Empty: ", nicer_test(); say "Nicer: One Item: ", nicer_test("sweet!"); say "Nicer: Two Items: ", nicer_test("dude!", "sweet!");

It evaluates the same, as far as I can tell.

Mean: Empty:
Mean: One Item: 1
Mean: Two Items: 1
Nicer: Empty:
Nicer: One Item: 1
Nicer: Two Items: 1

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Re^2: return !!
by massa (Hermit) on Mar 04, 2009 at 23:52 UTC
    The vim syntax highlighting thing can be fixed by putting a space between the bangs (! !@_).
    []s, HTH, Massa (κς,πμ,πλ)