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From: BrJohan <brjohan@gmail.com>
Newsgroups: comp.lang.python
Subject: Re: Python's re module and genealogy problem
Date: Fri, 13 Jun 2014 17:17:06 +0200
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On 11/06/2014 14:23, 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?

Thank you all for valuable input and interesting thoughts.

After having reconsidered my problem, it might be better to approach it 
a little differently.

Either to state the regexps simply like:
"(Kristina)|(Christina)|(Cristine)|(Kristine)"
instead of "((K|(Ch))ristina)|([CK]ristine)"

Or to put the namevariants in some sequence of sets having elements like:
("Kristina", "Christina", "Cristine", "Kristine")
Matching is then just applying the 'in' operator.

I see two distinct advantages.
1. Readability and maintainability
2. Any namevariant occurring in just one regexp or set means no risk of 
erroneous matching.

Comments?