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James Robertson http://www.r0bertson.co.uk

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Greedy vs Lazy in Regular Expressions

The greedy expression can be seen as a True *and* False predicate, meaning true while the token is valid, while being false if the pattern matching hasn't been exhausted.
The lazy expression is the True *or* False predicate, meaning true while the token is valid, or false if the pattern match hasn't been fully exhausted.

irb(main):037:0> "<EM>first</EM>"[/<.+>/] #greedy 
=> "<EM>first</EM>"
irb(main):038:0> "<EM>first</EM>"[/<.+?>/] #lazy
=> "<EM>"
irb(main):039:0> "<EM>first</EM>"[/<[^<>]+>/] # better solution
=> "<EM>"

source: Regular Expression Quick Start [regular-expressions.info]
to ruby regex pattern lazy matching greedy by jrobertson on Feb 04, 2008 3 Comments
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