| python Programming Glossary: dfaRegular Expressions in Python unexpectedly slow http://stackoverflow.com/questions/11190835/regular-expressions-in-python-unexpectedly-slow  when it fails to find a match as opposed to building a DFA and simulating it. It uses the backtracking approach even when.. 
 How can you detect if two regular expressions overlap in the strings they can match? http://stackoverflow.com/questions/1849447/how-can-you-detect-if-two-regular-expressions-overlap-in-the-strings-they-can-ma  standard decidability proof is to determinize them into DFA s first and then construct a new DFA whose states are pairs.. determinize them into DFA s first and then construct a new DFA whose states are pairs of the two DFAs' states and whose final.. then construct a new DFA whose states are pairs of the two DFAs' states and whose final states are exactly those in which both.. 
 How to tell if one regular expression matches a subset of another regular expression? http://stackoverflow.com/questions/6363397/how-to-tell-if-one-regular-expression-matches-a-subset-of-another-regular-expres  of B and also of the union A B . Check if the two DFAs are identical. This is true if and only if A matches a subset.. are explanations such as Constructing a minimum state DFA from a Regular Expression but they only tend to consider mathematically.. 
 What's the most efficient way to find one of several substrings in Python? http://stackoverflow.com/questions/842856/whats-the-most-efficient-way-to-find-one-of-several-substrings-in-python  conceptually the regular expression is modeled as a DFA and so as the input is consumed all matches are being tested.. 
 Python regular expression implementation details http://stackoverflow.com/questions/844183/python-regular-expression-implementation-details  I thought that regular expressions would be implemented as DFAs and therefore were very efficient requiring at most one scan.. a's as before . This clearly cannot be implemented with a DFA. So to reiterate what are the implementation details and guarantees.. 
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