Re: How to run index on this one?

index returns an offset from the beginning of the string, although I'm not really sure what you mean by "false position". For example:

use strict;
use warnings;

my $string='YYSFTVMETDPVN[115]HMVGVISVEGRPGLFWFN[115]ISGGDK';
my $offset = 0;
my $substring = 'N[115]';
my @positions;

while (1) {
    my $pos = index($string, $substring, $offset);
    last if $pos < 0;
    push @positions,$pos;
    $offset = $pos + length($substring);
}

print "Positions: @positions\n";
[download]

Gives:

Positions: 12 35
[download]

Comment on Re: How to run index on this one? Select or Download Code

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Re^2: How to run index on this one? by Anonymous Monk on Nov 25, 2009 at 15:23 UTC
Thanks for the reply! But, if you look at the string, I just want the position of 'N', without taking into consideration the `[115]` thing. In the code, you provided, it works ok for the first 'N', but for the second 'N', the correct position is 30 and not 35(this is because you count the first `[115]` and this increases the length of the string.	[reply] [d/l] [select]
Re^3: How to run index on this one? by cdarke (Prior) on Nov 25, 2009 at 15:31 UTC
OK. I said I didn't understand what you meant! How about this then (damn the hard-coded 5): `use strict; use warnings; my $string='YYSFTVMETDPVN[115]HMVGVISVEGRPGLFWFN[115]ISGGDKN[115]'; my $offset = 0; my $substring = 'N[115]'; my @positions; while (1) { my $pos = index($string, $substring, $offset); last if $pos < 0; $offset = $pos + length($substring); $pos -= 5 * @positions; push @positions,$pos; } print "Positions: @positions\n";` [download] Gives: `Positions: 12 30 37` [download] I added another N for testing. Update:I have recieved a /msg puzzling about a line of code. Here is a description of `$pos -= 5 * @positions;` We need to adjust the position by the length of `[115]` (5 characters), not just just once but for each position found. I use `@positions` in scalar context to get me the number of elements (scalar context is forced by the multiplication operator ). The first time around the loop the number of elements in `@positions` is zero, so `$pos` is not decremented. Subsequently it is decremented by 5 number-of-items-found.	[reply] [d/l] [select]