[Python-Dev] string.find() again (was Re: timsort for jython)

Andrew Koenig ark@research.att.com
07 Aug 2002 10:17:39 -0400

Tim>     re1 in re2

Tim> should be True iff the language accepted by re1 is a subset of
Tim> the language accepted by re2.  In this case, it's OK to consider
Tim> the empty language a subset of all others, since nobody will be
Tim> able to make head or tail out of the code anyway.

Note the distinction between the empty language and the empty string.
As a language is a set of strings, the empty language is one that
contains no strings, not even the empty string.  Therefore, a regular
expression that accepts the empty language is one that rejects every
string, even the empty string.

Pedantically y'rs    --ark