Thanks a lot! This is just what I was looking for in your first example.
(The second example won't do me as much good, as I need to consider
characters that haven't changed inside of a string of characters that
have--but it's still a good reference.)
Thanks again,
paul
10:11am, Rob Anderson wrote:
> > If anyone can offer general improvements to that approach, that'd be
> > great--but what I'm really interested in is finding the first element that
> > differs, and maybe the last as well. If there were any easy way to find
> > that, say, the first character that differs is at position 120, and the
> last
> > character that differs is at position 135, then I only have to loop
> through
> > 15 characters, not 160.
>
> Probably the quickest way to do this in perl is as follows....
>
> ----------------------------------------
> #!/perl -w
> use strict;
> my $string1 = "The quick brown fox.";
> my $string2 = "The Kuick brUwn fox.";
>
> my $string_xor = ("$string1" ^ "$string2");
>
> $string_xor =~ /^(\0*)/;
> print "Number of equal bytes at the front of the string = " . length($1) .
> "\n";
> $string_xor =~ /(\0*)$/;
> print "Number of equal bytes at the end of the string = " . length($1) .
> "\n";
> ----------------------------------------
>
> the xor op (^) will return a string, every matching byte of which will be
> null, every mismatching byte will have some bit (literaly) set.
>
> so the all first regex does is match the all the null bytes it can find from
> the front of the string, the length of the string is equivalent to the
> number of identical chars at the front.
> The second regex is the same, just working from the end.
>
> You could extend this and translate all the non-null values to something you
> could then search for that value with index. This would give you the
> positions of all the bytes that were different...
>
> my $string_xor = ("$string1" ^ "$string2");
> my $pos = 0;
> while ( ($pos = index($string_xor, 'X', $pos)) != -1) {
> print "==> $pos\n";
> $pos++;
> }
>
> Hope this helps,
>
> Rob
>
> >
> > TIA,
> >
> > paul
> >
> >
> > ---------------------------------------------------------------------
> > On the side of the software box, in the "System Requirements" section,
> > it said "Requires Windows 95 or better". So I installed Linux.
> > ---------------------------------------------------------------------
>
>
>
-----------------------------------------------------
"Somebody did say Swedish porn, there--
but someone always does..."
--Clive Anderson, host of "Whose Line Is It, Anyway",
after asking the audience for movie suggestions
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