# About regexp

**URL:** <https://www.ruby-forum.com/t/about-regexp/149168>\
**Category:** Ruby\
**Created:** [September 22, 2008, 8:09am UTC](https://www.ruby-forum.com/t/about-regexp/149168 "2008-09-22T08:09:34Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Kyung\_won\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/47e85d/32.png) [@Kyung\_won\_C](https://www.ruby-forum.com/u/Kyung_won_C)\
**Post date:** [September 22, 2008, 8:09am UTC](https://www.ruby-forum.com/t/about-regexp/149168/1 "2008-09-22T08:09:34Z")

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> > “a 1 b”.sub(/\b1\b/, “2”)  
> > =\> “a 2 b”
> 
> > “a \* b”.sub(/\b\*\b/, “2”)  
> > =\> “a \* b” # Why not “a 2 b” ???

How ??

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# Help Me^^

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**Author:** ![Kyung\_won\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/47e85d/32.png) [@Kyung\_won\_C](https://www.ruby-forum.com/u/Kyung_won_C)\
**Post date:** [September 22, 2008, 9:20am UTC](https://www.ruby-forum.com/t/about-regexp/149168/2 "2008-09-22T09:20:49Z")

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2008/9/22 Kyung won Cheon [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid):

> > > “a 1 b”.sub(/\b1\b/, “2”)  
> > > =\> “a 2 b”  
> > > “a \* b”.sub(/\b\*\b/, “2”)  
> > > =\> “a \* b” # Why not “a 2 b” ???
> 
> How ??

Because neither " _" nor "_ " are word boundaries.

Cheers

robert

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**Author:** ![Kyung\_won\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/47e85d/32.png) [@Kyung\_won\_C](https://www.ruby-forum.com/u/Kyung_won_C)\
**Post date:** [September 22, 2008, 9:24am UTC](https://www.ruby-forum.com/t/about-regexp/149168/3 "2008-09-22T09:24:19Z")

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/\*/ is a non-word character.