Ruby RegEx not matching valid expression

Posted by Matthew Carriere on Stack Overflow See other posts from Stack Overflow or by Matthew Carriere
Published on 2010-05-08T00:57:04Z Indexed on 2010/05/08 0:58 UTC
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ruby

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regex

I have the following expression:

^\w(\s(+|-|\/|*)\s\w)*$

This simply looks to match a mathematical expression, where a user is prompted for terms separated by basic operators (ex: price + tax)

The user may enter more than just 2 terms and one operator (ex: price + tax + moretax)

I tested this expression in Rubular http://rubular.com/

With the terms:

a + a (MATCH) a + a + a (MATCH) a + a + a + a a a + a a

Everything works, but when I use it in Ruby it does not work!

expression =~ /^\w(\s(+|-|\/|*)\s\w)*$/

I started picking the expression apart and noticed that if I remove the start of line caret it finds matches but isn't correct.

a + a (MATCH) a a (MATCH) <-- this is not correct

Why is this expression not working in Ruby code? (I am using Ruby 1.8.7 p174)

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