Reverse engineering regular expressions

Any questions involving matching text strings to patterns - the pattern is called a "regular expression."

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wonderoid
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Joined: Tue Oct 13, 2009 2:36 pm

Reverse engineering regular expressions

Post by wonderoid »

Hello;

Assume that I have a url in the form:

"item/a=5/b=5" and I am using a regular expression to capture the numbers in it with two groups of ([0-9]+). Now what I want to be able to do is reverse engineer this regexp for lets say 6 and 7 and get the url "item/a=6/b=7" back.

I know this can be done manually with string operations but I wanted to learn if it can be done using the regex itself.

The reason I want to do this is; I am trying to write my own url routing method. Lets say I map /products/3 to a controller ProductsController, action listAction add a parameter id = 3. I want to be able to create valid urls using a utility function createUrl($controller, $action, $params) by reverse engineering the regexp and replacing the groups with their new values.

Thanks.
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