in reply to Re: Alternative matches
in thread Alternative matches

No.
1) You wouldn't want to chain so many calls to index (its like writing $array[0]=3; $array[1]=4; $array[1]=5;)

2) Notice the use of capturing parenthises? It means that kiat wants to know what word he matched. To do that with index gets ugly real fast, for example 

my @words = qw[ new old number start simple cross heavy die exit ];
my $string = q~whatever the NEw old you're trying to match~;
my $lcstring = lc $string;
my $ret = 0;
if( do {
        for my $val( @words ){
            my $r = index $lcstring, $val;
            if( $r > -1 ){
                $ret = substr $string, $r, length $val;
                last;
            }
        }
        $ret;
    } ){
    warn "the \$1 (aka ret) is => $ret\n\n";
}
__END__
the $1 (aka ret) is => NEw

[download]
Granted you could turn that do{} into a function, but I don't think its worth the effort (even if there may be a slight speed boost).

MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"
I run a Win32 PPM repository for perl 5.6.x and 5.8.x -- I take requests (README).
** The third rule of perl club is a statement of fact: pod is sexy.

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Re^3: Alternative matches
by foss_city (Novice) on Oct 06, 2004 at 11:45 UTC
    Oops. i missed the capturing parentheses . . . . *blushes* However, outside of that, i'm not clear on why one wouldn't want to do something like: 
        if ( index($string, 'new')    ||
        index($string, 'old')    ||
        index($string, 'number') ||
        # etc.
       ) { # etc. }

    [download]
    except that it does seem ugly to me, now i look at it. :-) Could you elaborate, please?
[reply]
[d/l]
      *boggle* Take a look at Re^2: Alternative matches again. Then try perldoc -f index.
      What you'd need to actually write is 
      index($string,'new') > -1 ||

      [download]
      for however many words there are. You'd have to modify that if for every new word you added, which would soon turn into 
      index($string,'new') > -1 ||

index($string,'old') > -1 ||

index($string,'number') > -1 ||

index($string,'start') > -1 ||

index($string,'simple') > -1 ||

index($string,'cross') > -1 ||

index($string,'heavy') > -1 ||

index($string,'die') > -1 ||

index($string,'exit') > -1 || ...

      [download]
      That is a lot of cut'n'pasting and this is not what programmers do. What you'd do is write a function to loop over an array like I did.

      MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"
      I run a Win32 PPM repository for perl 5.6.x and 5.8.x -- I take requests (README).
      ** The third rule of perl club is a statement of fact: pod is sexy.

[reply]
[d/l]
[select]
        I wrote this code assuming the regexp would still be faster, and I wanted to prove it. I was shocked by what I found. I'm borrowing some of PodMaster's benchmark code. If there's something wrong with my testing let me know, but it sure looks like the index solution blows the regexp out of the water. 
        #!/usr/bin/perl
use strict;
use warnings;
 
use Benchmark 'cmpthese';
use List::Util 'first';
 
my @words = qw[ new old number start simple cross heavy die exit ];
my $string = join ' 0\4/f ', map( { rand $_ } 1 .. 60), map { $words[ 
+rand @words ] } 1 .. 20;
 
cmpthese (-3, {
        regexp => sub {
            return $string =~ /(new|old|number|start|simple|cross|heav
+y|die|exit)/i;
        },
        use_index => sub {
            my $lcstring = lc $string;
            return first {index($lcstring, $_) > -1} @words;
        }
});

__END__
             Rate    regexp use_index
regexp     1084/s        --      -96%
use_index 29469/s     2619%        --

        [download]
[reply]
[d/l]
[select]
        Thanks for clarifying that. But i wonder, do Real Programmers also try to avoid making assumptions about what they're working with? Because i think you meant to tell me to try man perlfunc . . . . or indeed, to read the Camel more carefully. i'm tired and lacking in concentration tonight; i think i'll take my pseudo-programmer self away and just spectate from now on.
[reply]
[d/l]
Re^3: Alternative matches
by Jasper (Chaplain) on Oct 06, 2004 at 12:24 UTC
    Err... 

    $r = index $lcstring, $val;;
$ret = substr $string, $r, length $val;

    [download]
    Seems like a very obfuscated way of saying $ret = $val if -1 < index $lcstring, $val;
    No?
[reply]
[d/l]
[select]
      No. Pay attention:
      my $string = q~whatever the NEw old you're trying to match~;

      my $lcstring = lc $string;

      the $1 (aka ret) is => NEw

      $string ne lc $string

      MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"
      I run a Win32 PPM repository for perl 5.6.x and 5.8.x -- I take requests (README).
      ** The third rule of perl club is a statement of fact: pod is sexy.

[reply]

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