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Regular Expression For Consecutive Duplicate Words

Answer 1

+2 A:

No. That is an irregular grammar. There may be engine-/language-specific regular expressions that you can use, but there is no universal regular expression that can do that.

Ignacio Vazquez-Abrams 2010-05-12 21:53:15

Though being correct in a strict sense, I believe there is no regex engine in serious use anymore that does not support grouping and back-references.

Tomalak 2010-05-12 22:35:43

Answer 2

+4 A:

Try this regular expression:

\b(\w+)\s+\1\b

Here \b is a word boundary and \1 references the captured match of the first group.

Gumbo 2010-05-12 21:55:01

Makes me wonder; is it possible to do `\0` too? (Where `\0` is the whole regex, up to the current point OR where `\0` refers to the whole regex)

Pindatjuh 2010-05-12 22:37:31

@Pindatjuh: No, I don’t think so because that sub-match would also be part of the whole match.

Gumbo 2010-05-12 22:40:34

Answer 3

+2 A:

The widely-used PCRE library can handle such situations (you won't achieve the the same with POSIX-compliant regex engines, though):

(\b\w+\b)\W+\1

soulmerge 2010-05-12 21:55:46

You need something to match the characters *between* the two words, like `\W+`. `\b` won't do it, because it doesn't consume any characters.

Alan Moore 2010-05-12 22:35:23

Many thanks, fixed.

soulmerge 2010-05-13 09:16:13

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Regular Expression For Consecutive Duplicate Words

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