in reply to Badly need to call a function...:-)

I have to know. Why would someone use "if 1 == 1"? Is that part of the obfuscation or is it actually in the code?

($_='kkvvttuu bbooppuuiiffss qqffssmm iibbddllffss')
=~y~b-v~a-z~s; print
  • Comment on Re: Badly need to call a function...:-)

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Re^2: Badly need to call a function...:-)
by eibwen (Friar) on Apr 17, 2005 at 00:13 UTC
    As far as I can tell, if (1==1) { } is being used as an alternative to commenting out the lines. While this may provide a simple way to skip a block of code by changing a single character, there appears to be a performance detriment: 

    #!/usr/bin/perl -w

use strict;

if (1==1) { 1; }

    [download]
    $ perl -MO=Deparse equal

BEGIN { $^W = 1; }
use strict 'refs';
do {
    '???':
};

    [download]
    #!/usr/bin/perl -w

use strict;

if (0==1) { 1; }

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    $ perl -MO=Deparse unequal

BEGIN { $^W = 1; }
use strict 'refs';
do {
    '???'
};

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    #!/usr/bin/perl -w

use strict;

if (1==0) { 1; }

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    $ perl -MO=Deparse unequal2

BEGIN { $^W = 1; }
use strict 'refs';
do {
    '???'
};

    [download]

    #!/usr/bin/perl -w

use strict;

1;

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    $ perl -MO=Deparse uncommented

BEGIN { $^W = 1; }
use strict 'refs';
'???':

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    #!/usr/bin/perl -w

use strict;

# 1;

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    $ perl -MO=Deparse commented

BEGIN { $^W = 1; }

    [download]

    UPDATE: Added the if (1==1) { } corollary

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Re^2: Badly need to call a function...:-)
by Mabooka-Mabooka (Sexton) on Apr 17, 2005 at 05:25 UTC
    Dear pedant and all gurus: I am very pleased with your attention, didn't expect anything like that.
    regarding (1==1): gentlement, c'mon, I only wanted to "kind-of-preserve" the "if" statement without exposing the business logic.
    Greately surprised that this sort of things can have a performance implications. From the other hand, curious: can these tiny details have an impact on real-world stuff?
[reply]
      The performance implication depends on your implementation. If it's a critical application, particularly one that iterates significantly, the difference may be significant. Conversely, if the code isn't iterative, or only sees a few iterations, the difference is likely neglible. Given this understanding, you may want to benchmark the codes using the Benchmark module: 

      use Benchmark qw(cmpthese);

@data = (1,2,3,4); # the values that would have been in @_

my $minCPUsec = 15;

cmpthese(-$minCPUsec, {
  with =>    \&sub_with_ifs,
  without => \&sub_without_ifs
});

      [download]

      And change @_ in the referenced subs to @data.

      Additionally, you may be interested in the Benchmarking Your Code tutorial, but I'd recommend using cmpthese instead of timethese.

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