Wow. We're even getting polysyllabic pissing matches on the Edu list. Way cool. <big wink> --- Patrick K. O'Brien Orbtech "I am, therefore I think." -----Original Message----- From: edu-sig-admin@python.org [mailto:edu-sig-admin@python.org]On Behalf Of Tim Peters Sent: Sunday, May 27, 2001 2:44 PM To: edu-sig@python.org Subject: RE: [Edu-sig] Re: Lisp vs Scheme vs Python [Matthias Felleisen]
... Recursion: Read up on data types and how to specify them. Mathematically speaking (and that's what you want to do), there are
basic sets subsets unions products inductive definitions (co-inductive definitions).
That's it.
I'd add finite maps to the list, aka associative arrays ("dictionaries" in Python). Viewing a finite map as a subset of the product of the key and value sets isn't particularly illuminating, and especially not in a programming context. You can object that it's not "primitive", but then neither are products: in set theory products are defined in terms of ordered pairs, where ordered pairs are in turn defined in terms of unordered sets, the ordered pair (a, b) being (by definition) the set {{a}, {a, b}}. Since products are frequent in practice, that reduction is too tedious to endure every time, so we agree to pretend products are primitive in order to get on with life. Finite maps are also useful enough to merit (pseudo)primitive status. <much more snipped>