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Re: Sliding window

by Eliya (Vicar)
on Jan 27, 2012 at 14:59 UTC ( #950383=note: print w/replies, xml ) Need Help??


in reply to Sliding window

As I understand your task (which seems to be different from BrowserUk), this should do it:

#!/usr/bin/perl -w use strict; my %hash = (a=>2, b=>1, c=>5, d=>3, e=>4); my $input = "abcdaeec"; for (2, 3) { print "n=$_: "; my $n = $_ - 1; my @sums; while ( $input =~ /(.)(?=.{$n}(.))/g ) { push @sums, $hash{$1} + $hash{$2}; } print "@sums\n"; } __END__ n=2: 7 4 7 7 6 9 n=3: 5 3 9 7 7

Update: let YAPE::Regex::Explain explain what the regex does:

use YAPE::Regex::Explain; print YAPE::Regex::Explain->new( qr/(.)(?=.{1}(.))/ )->explain; __END__ The regular expression: (?-imsx:(.)(?=.{1}(.))) matches as follows: NODE EXPLANATION ---------------------------------------------------------------------- (?-imsx: group, but do not capture (case-sensitive) (with ^ and $ matching normally) (with . not matching \n) (matching whitespace and # normally): ---------------------------------------------------------------------- ( group and capture to \1: ---------------------------------------------------------------------- . any character except \n ---------------------------------------------------------------------- ) end of \1 ---------------------------------------------------------------------- (?= look ahead to see if there is: ---------------------------------------------------------------------- .{1} any character except \n (1 times) ---------------------------------------------------------------------- ( group and capture to \2: ---------------------------------------------------------------------- . any character except \n ---------------------------------------------------------------------- ) end of \2 ---------------------------------------------------------------------- ) end of look-ahead ---------------------------------------------------------------------- ) end of grouping ----------------------------------------------------------------------

And see perlop for what m//g does in scalar context (like the while (...) here).

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