Re: Unusual Closure Behaviour

HI, Try this, Here it says that $x is not defined and therefore it creates a new local variable $x with 'my'.
Otherwise it uses the last value of x which is the default behaviour.


sub foo {
        my $x if !defined $x;
        return ++$x;
}
for (1..7){ print foo(); };
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Comment on Re: Unusual Closure Behaviour Download Code

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(tye)Re2: Unusual Closure Behaviour
by tye (Sage) on Jul 13, 2001 at 03:20 UTC

Actually, that code isn't doing what you think. One way to see is to just add "use strict" to it. You'll get: Global symbol "$x" requires explicit package name

A more fun way is:

sub foo {
    my $x= $_[0]   if  ! defined $x;
    print "(@_):", ++$x, " ";
    undef $x   if  @_  &&  shift;
}
foo($_) for( 0,0,5,4,3,0,5,0,4,0,3 );
print $/, $x= 10, $/;
foo($_) for( 0,0,5,4,3,0,5,0,4,0,3 );
print $/;
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(0):1 (0):1 (5):6 (4):5 (3):4 (0):1 (5):6 (0):1 (4):5 (0):1 (3):4
10
(0):1 (0):2 (5):3 (4):1 (3):1 (0):1 (5):2 (0):1 (4):2 (0):1 (3):2
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end

So your code is always initializing the lexical $x in your subroutine because you have never defined the global $main::x that you are checking against.

tye

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