String replacement

wallacei has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks,
I would like to place "-" into string A based on the position they are in string B.
Basic Idea: ABABA goes to AB--A-BA based on template BB--B-BB
I can do this just by looping over the two strings, as below, but I am wondering if there is a neat perl way of doing it with out using loops? Thanks for your guidance!

  my $j =0;
        for($i=0;$i<length($protein);$i++){
        my $chr=substr($protein,$i,1);
                if($chr ne "-"){
                        $new_dna=$new_dna.substr($dna,$j,1);
                        $j=$j+1;
                }else{
                        $new_dna=$new_dna."-";
                } 
                                                                      
+                                                                     
+                                                                     
+                                  }
[download]

Comment on String replacement Download Code

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Re: String replacement by Tanalis (Curate) on Jul 21, 2005 at 14:30 UTC
Probably not the best way to do it, but this works: `my $a = "ABABA"; my $b = "BB--B-BB"; $b =~ s/B/\%c/g; printf $b, unpack 'c', $a;` [download] Gets rid of the loop, at least grin*. -- Foxcub `#include www.liquidfusion.org.uk`	[reply] [d/l]
Re: String replacement by Roy Johnson (Monsignor) on Jul 21, 2005 at 18:53 UTC
This is the same as what you're doing, but using s/// to walk the template. `my $a = "ABABA"; my $b = "BB--B-BB"; my $new = $b; my $a_pos = 0; $new =~ s:[^-]:substr($a, $a_pos++, 1):ge; print "New is $new\n";` [download] Update: I like this better. Inserting hyphens at corresponding points: `my $a = "ABABA"; my $b = "BB--B-BB"; substr($a, pos($b)-1, 0, '-') while ($b =~ /-/g); print "A is now $a\n";` [download] Caution: Contents may have been coded under pressure.	[reply] [d/l] [select]
Re: String replacement by radiantmatrix (Parson) on Jul 21, 2005 at 20:15 UTC
Yet another WTDI: `my ($string_a, $string_b) = ('ABABA','BB--B-BB'); my @a = split '',$string_a; my @b = split '',$string_b; $string_a = ''; my $a_ndx = 0; for (0..@b-1) { $string_a .= $b[$_] eq '-' ? '-' : $a[$a_ndx++] }` [download] This particular version modifies the 'A' string, but it could be trivially modified to preserve that string and build a fresh one; I consider that an advantage, but YMMV. <-radiant.matrix-> Larry Wall is Yoda: there is no `try{}` (ok, except in Perl6; way to ruin a joke, Larry! ;P) The Code that can be seen is not the true Code "In any sufficiently large group of people, most are idiots" - Kaa's Law	[reply] [d/l]