Re: This should be easy: counting letters in a string


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Re: This should be easy: counting letters in a string

by inman (Curate)

on Jan 31, 2006 at 11:36 UTC ( [id://526714]=note: print w/replies, xml )

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in reply to This should be easy: counting letters in a string

The transliteration does not interpolate the variable as you expect in your sample. The following illustrates the use of eval.

use strict;
use warnings;

my @letters = qw (A B C D E F);
my $string = "AFTYUBEWTWECRTUTYIYTDDDDRYJURTHJTREEEEEFGSDFF";
my $count;
foreach my $a(@letters) {
    eval "\$count = \$string =~ tr/$a//";
    print "$count\n";
}
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You can also use a substitution in order to interpolate but avoid the eval.

$count = $string =~ s/$a//g;
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Both methods change the string. A more flexible way to count the values would be to split the string and use a hash to store the values.

my %count;
$count{$_}++ foreach split //, $string;
print "$count{$_}\n" foreach (@letters);
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Re^2: This should be easy: counting letters in a string
by Roy Johnson (Monsignor) on Jan 31, 2006 at 14:46 UTC

Both methods change the string.

tr/a//

d

And using a little trick to induce list context, you can use pattern matching to count the occurrences:

my @letters = qw(A B C D E F);

my $string = 'AFTYUBEWTWECRTUTYIYTDDDDRYJURTHJTREEEEEFGSDFF';

my @counts;

for (0..$#letters) {
  $counts[$_] = () = $string =~ /$letters[$_]/g;
}

print "@counts\n";
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