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alphanumeric - finding one less!

Posted on 2002-05-08
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Last Modified: 2010-03-05
Hi

I need some help to chamge the end character in a string of letters to the character or number which is one less based on alphanumeric characters and maintaining case

example string 1 - " /YEZ/NOZ1/B2FREE/fixed "
example string 2 - " /YEZ/NOZ1/B2FRE3/fixed "

I want to become

example string 1 - " /YEZ/NOZ1/B2FRED/fixed "
example string 2 - " /YEZ/NOZ1/B2FRE2/fixed "

I have tried using "$string =~ s/$end/$end -1/"

but it doesn't work becase it is not a number and sometimes it finishes with "a letter/fixed" sometimes "a number/fixed"

"fixed" is the known string which is always constant...
"/APHANUM/APHANUM/APHANUM/" is the dynamic bit and it is always the character before "/fixed" that I need to be one less...

Can anyone tell me how to do it?

thanks

Jilly  
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Question by:jillybabe
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Accepted Solution

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holli earned 100 total points
ID: 6996554
this is one way:

$b="/YEZ/NOZ1/B2FREE/fixed";
$a="/YEZ/NOZ1/B2FRE3/fixed";

$a=~s|(.{1})/fixed|chr(ord($1)-1).'/fixed'|e;
$b=~s|(.{1})/fixed|chr(ord($1)-1).'/fixed'|e;

print "$a\$b";


regards,

holli
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Expert Comment

by:japhyRPI
ID: 6998068
What should "BAA" decrease to?  "AZZ"?  And how about "FR0"?  That's a zero, so should it be "FQ9"?  We need more assistance with these boundary cases.  It's far easier to INCREMENT than to decrement.
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Author Comment

by:jillybabe
ID: 6998242
Great that did it !

Thanks holli and you too japhyRPI

Jilly
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Expert Comment

by:japhyRPI
ID: 6998715
Jilly, I'm just warning you that the current response turns "BAA" into "BA@", "FR0" into "FR/", and "STa" into "ST`".  To overcome these situations, you're going to need a slightly different regex.
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