stylistic question -- optional return value

[Andrew Koenig]

Bengt> What about defining a class to represent the "data structure,"
Bengt> and passing a reference to an instance of that to your various
Bengt> routines, so that they can populate the structure themselves
Bengt> (via methods/attributes/properties as convenient) instead of
Bengt> returning data for a caller to do the populating with?

That's certainly a possibility, but it's a little heavyweight.

Of the various alternatives I've heard so far, the one I like best is simply
using None to represent the optional information.  That is, I return either
(x, y) or (x, None) depending on whether y exists.

Bengt> BTW, you mentioned recursion in another part of the thread. Is
Bengt> that as in recursive descent? An exception is an interesting
Bengt> alternative way to return a first match, with no need to return
Bengt> anything from unsuccessful visits.

Yes, it is a species of recursive descent.  What I'm doing, though,
is returning generators at each stage.  That way I cover all of the
possibilities.

-- 
Andrew Koenig, ark at research.att.com, http://www.research.att.com/info/ark