Regular expressions question

[Joseph Czapski]

Hi. You know that special character \b (word border) that is handy to use
because it does not eat a character that you might want to match to another
piece of your expression? \b matches the start or finish of a string of
word characters: letters, numbers, and _. Is there any way to match the
border of an arbitrary set of characters, also without eating a character?
For example, say I want to match to the beginning or end of a string of the
letters A, S, D, or F.

Thanks very much.

Joe Czapski
Boston, Mass.

[Jim Gibson]

Re: Regular expressions question

In article <y6ydnQns76U_KZ 7eRVn-1Q@comcast.com> , Joseph Czapski
<joec@nnnot.com > wrote:
[color=blue]
> Hi. You know that special character \b (word border) that is handy to use
> because it does not eat a character that you might want to match to another
> piece of your expression? \b matches the start or finish of a string of
> word characters: letters, numbers, and _. Is there any way to match the
> border of an arbitrary set of characters, also without eating a character?
> For example, say I want to match to the beginning or end of a string of the
> letters A, S, D, or F.[/color]

Your question doesn't make a lot of sense to me. The regex /[ASDF]+/
will match one or more of those characters in consecutive positions in
a string. The characters immediately before and after will not be one
of ASDF. Can you give some examples of what you are trying to match,
with some sample strings that match and some that do not?

You can use "zero-width negative lookahead (?=...) and -behind (?!...)"
assertions to customize what should precede and follow any match, if
that helps.

FYI: this newsgroup is defunct; try comp.lang.perl. misc in the future.


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