substring and regular expression

Diez B.Roggisch deets at web.de
Thu Aug 4 20:56:03 CEST 2005


borges2003xx <at> yahoo.it <borges2003xx <at> yahoo.it> writes:

> 
> but in general is there a way to include in a re, in this example
> something like...matches iff p , and q in which p==q[::-1] ? A way to
> putting a small part of code of python in re? Thanx for your many helps

What you are after is a parser - there are plenty available. I prefer spark, but 
pyparsing has gained lots of attention lately and is AFAIK the quasi-standard.

The problem you described is a classical instance of a so-called
 context-free grammar.
There is absolutely _no_ way to teach regular expressions how to detect words 
created based on a grammar of that kind. Really. It won't work.

So - either use a parser, or write a simple one yourself - the code above 
qualifies as  an attempt to do so.

Regards,

Diez




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