Python's re module and genealogy problem

[Robert Kern]

On 2014-06-11 13:23, BrJohan wrote:
> For some genealogical purposes I consider using Python's re module.
>
> Rather many names can be spelled in a number of similar ways, and in order to
> match names even if they are spelled differently, I will build regular
> expressions, each of which is supposed to match  a number of similar names.
>
> I guess that there will be a few hundred such regular expressions covering most
> popular names.
>
> Now, my problem: Is there a way to decide whether any two - or more - of those
> regular expressions will match the same string?
>
> Or, stated a little differently:
>
> Can it, for a pair of regular expressions be decided whether at least one string
> matching both of those regular expressions, can be constructed?
>
> If it is possible to make such a decision, then how? Anyone aware of an
> algorithm for this?

And if that isn't the best straight line for the old saying, I don't know what is.

   http://en.wikiquote.org/wiki/Jamie_Zawinski

Anyways, to your new problem, yes it's possible. Search for "regular expression 
intersection" for possible approaches. You will probably have to translate the 
regular expression to a different formalism or at least a different library to 
implement this.

Consider just listing out the different possibilities. All of your regexes 
should be "well-behaved" given the constraints of the domain (tightly bounded, 
at least). There are tools that help generate matching strings from a Python 
regex. This will help you QA your regexes, too, to be sure that they match what 
you expect them to and not match non-names.

   https://github.com/asciimoo/exrex

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco