Created
July 14, 2013 15:57
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Lookahead and Lookbehind Assertions
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| # Lookahead assertion | |
| str = "123 456. 789" | |
| m = /\d+(?=\.)/.match(str) # m[0] = '456'. Period doesn't count as a part of the match | |
| /\d+(?!\.)/ # negative lookahead | |
| # Lookbehind assertion | |
| str = "David BLACK" | |
| m = /(?<=David )BLACK/ # only match BLACK if it's preceded by 'David' | |
| /(?<!David) BLACK/ # negative lookbehind | |
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