in reply to Re^5: Undefined vs empty string
in thread Undefined vs empty string

Wrong impression. If you look at the figures, there is no difference between '0', '1' and "xxxx…". I known the speed of length doesn't depend on the length of the PV (unless of course it is overloaded or magic). I was actually kind of hoping that the example showed just that.


Enjoy, Have FUN! H.Merijn

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Re^7: Undefined vs empty string
by BrowserUk (Patriarch) on Jun 05, 2013 at 11:57 UTC
    I was actually kind of hoping that the example showed just that.

    Here's an even mix of possible values including the empty string which you omitted, and the results are too close to call.:

    #! perl -slw
use strict;
use Benchmark qw[ cmpthese ];

our @tests = (
    (undef)  x1000,
    ('')     x1000,
    (chr(0)) x1000,
    (0)      x1000,
    (1)      x1000,
    ('fred') x1000,
);
cmpthese -1, {
    a => q[ !(defined && length() ) and 1 for @tests; ],
    b => q[ !defined || $_ eq ''    and 1 for @tests; ],
};

__END__
C:\test>junk
    Rate    b    a
b 1029/s   -- -17%
a 1239/s  20%   --

C:\test>junk
    Rate   b   a
b 1065/s  -- -1%
a 1079/s  1%  --

    [download]

    Much of a muchness.

    I guess you could get into varying the proportions of the mix commensurate with your application expectations, but ...

    With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]
[d/l]

      How does my defined-or solution compare on your system?

      Where did I omit the empty string in

      foreach $a (undef, "", 0, 1, "x" x 60) {

      ?

      update new bench from your example. (my dor outperforms the other two consistently)

      $ cat test.pl
use strict;
use Benchmark qw[ cmpthese ];

our @tests = (
    (undef)  x 1000,
    ("")     x 1000,
    (chr(0)) x 1000,
    (0)      x 1000,
    (1)      x 1000,
    ("fred") x 1000,
    );
cmpthese -1, {
    a => q[ !(defined && length() ) and 1 for @tests; ],
    b => q[ !defined || $_ eq ""    and 1 for @tests; ],
    c => q[ ($_ // "") eq ""        and 1 for @tests; ],
    };
$ repeat 5 perl test.pl
    Rate    b    a    c
b 1950/s   -- -18% -33%
a 2379/s  22%   -- -18%
c 2901/s  49%  22%   --
    Rate    b    a    c
b 1950/s   -- -22% -33%
a 2511/s  29%   -- -13%
c 2901/s  49%  16%   --
    Rate    b    a    c
b 1950/s   -- -23% -32%
a 2536/s  30%   -- -12%
c 2875/s  47%  13%   --
    Rate    b    a    c
b 1914/s   -- -22% -32%
a 2466/s  29%   -- -12%
c 2801/s  46%  14%   --
    Rate    b    a    c
b 1950/s   -- -23% -32%
a 2536/s  30%   -- -12%
c 2875/s  47%  13%   --

      [download]

      Enjoy, Have FUN! H.Merijn
[reply]
[d/l]
[select]
        Where did I omit the empty string in

        Damn. My eyes are getting like an old CRT. They are taking longer and longer to warm up in the mornings :)

        With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
        Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
        "Science is about questioning the status quo. Questioning authority".
        In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]

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