in reply to substr function

Search for pp_substr in pp.c.

It's not a good idea to want to modify substr on that level. You can use subs (I think) and override substr with your own custom function. That makes it still a bad idea, but at least you can write your replacement in Perl that way.

What problem are you trying to solve that involves replacing substr?

Update: subs seems to be the wrong module, but I'm sure I remember a module that allowed one to replace built-ins. Maybe I'm just thinking of CORE::GLOBAL:: though:

BEGIN{
    *CORE::GLOBAL::substr=sub($$$) { die };
}
print substr 'foo',2,3;

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Re^2: substr function
by tej (Scribe) on Jan 13, 2011 at 15:02 UTC

    I want to understand how it is working and then write my own subroutine for my script

    Suppose i have string that contains tags like "<bold>" it should not count this tag. If string has something like "<194>" I want substr to consider it as one character.

    Thank you very much

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      Then write your own implementation of substr instead of replacing it. Most likely you'll need to write a parser for whatever language you're parsing. It shouldn't be hard, and "replace substr" clutters your problem with many hard (and weird) problems that are unrelated to the task.

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[d/l]

      Write an ordinary Perl program that filters the text, then measures its length using the built-in substr function.

      You're trying to solve an everyday text processing problem in a very peculiar and unconventional way. Writing a custom substr function to measure a particular kind of "string" is like inventing a bathroom scale that knows when your hair is wet and you haven't removed your shoes, yet accurately measures your bone-dry, barefoot weight.

      I'm curious: Do you want to measure the lengths of the strings in bytes, in encoded characters (Unicode code points), or in real-world characters (Unicode extended grapheme clusters)?

      CLARIFICATION: I admit I sort of conflated substr and length in this post. My excuse is that I was fixated on the words "count" and "one character" in tej's restatement of his Y problem:

      Suppose i have string that contains tags like "<bold>" it should not count this tag. If string has something like "<194>" I want substr to consider it as one character.
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[d/l]
        I suspect <194> refers to a character, and that this notation is used for non-ASCII characters. If so, your last question is moot.
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[d/l]

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