Regular expression listing all possibilities

Question

Given a regular expression, how can I list all possible matches? For example: AB[CD]1234, I want it to return a list like: ABC1234 ABD1234

I searched the web, but co

Answer 1

It's possible to write an algorithm to do this but it will only work for regular expressions that have a finite set of possible matches. Your regexes would be limited to using:

• Optional: ?
• Characters: . \d \D
• Sets: like [1a-c]
• Negated sets: [^2-9d-z]
• Alternations: |
• Positive lookarounds

So your regexes could NOT use:

• Repeaters: * +
• Word patterns: \w \W
• Negative lookarounds
• Some zero-width assertions: ^ $

And there are some others (word boundaries, lazy & greedy quantifiers) I'm not sure about yet.

As for the algorithm itself, another user posted a link to this answer which describes how to create it.