in reply to Re: doing tr/// on-the-fly?
in thread doing tr/// on-the-fly?

Extending this to get the number of substitutions... 
my $result;
eval "\$result = \$s =~ tr/$search/$replace/";

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Also, the OP would have gotten warning messages with use warnings;

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Re^3: doing tr/// on-the-fly?
by Anonymous Monk on Mar 18, 2010 at 01:37 UTC

    Thanks. That is useful information to have.

    Any information on CPAN modules to use for escaping? It would really help if something were installed by default. :)

[reply]
      Dynamic tr is kind of nonsensical, just use s///, it will be just as fast
[reply]
        just use s///, it will be just as fast

        Not even close: 

        $from = 'abcd'; $to = '1234';;
@t = map 'axbxcxdx' x 10, 1 .. 1000;;

cmpthese -1,
{
    tr => q[
        my $tr = eval "sub{ \$_[0] =~ tr[$from][$to] }"; 
        $tr->( $_ ) for @{[ @t ]}; 
    ],
    s  => q[ 
        my %tr; @tr{ split'', $from } = split'', $to; 
        s[([$from])]{ $tr{$1} }eg for @{[@t]} 
    ],
};;

     Rate     s    tr
s  32.0/s    --  -97%
tr 1054/s 3189%    --


@t = map 'axbxcxdx' x 1000, 1 .. 1000;;

cmpthese -1,
{
    tr => q[
        my $tr = eval "sub{ \$_[0] =~ tr[$from][$to] }"; 
        $tr->( $_ ) for @{[ @t ]}; 
    ],
    s  => q[ 
        my %tr; @tr{ split'', $from } = split'', $to; 
        s[([$from])]{ $tr{$1} }eg for @{[@t]} 
    ],
};;
            (warning: too few iterations for a reliable count)

      s/iter      s     tr
s       2.65     --   -99%
tr 1.98e-002 13317%     --

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        "Science is about questioning the status quo. Questioning authority".
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