in reply to Alternative matches

Isn't index() often faster for this sort of fixed-string search? If so, would it be better to chain a series of calls to index() with the || operator? (Except that since you want case-insensitivity, you would want to lc($string) first.) Just pondering . . . .

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Re^2: Alternative matches
by PodMaster (Abbot) on Oct 06, 2004 at 11:18 UTC
    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.

[reply]
[d/l]
[select]
      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]
      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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