>why do you say "can't use" we can can just *redefine*
Oh, definitely. I agree. We certainly can and SHOULD have students learn to
redefine what we mean by various operators. In saying "can't use" I don't mean
"can't EVER use". : ) I just mean within the scope of this exercise. Again,
I initially meant this to be an exercise PRIOR to studying any particular
language. I think it's a good kind of math/CS exercise to have to analyze what
we mean by simple integer operations that we normally take for granted, and
this analysis naturally introduces recursion. And I think it nicely blends in
with ultimately redefining these operations for other data structures.
>But in Python, we have been, given looping constructs
Right. Again, I just mean within the scope of the exercise.
Along this line, here's an interesting thing regarding GCF - suppose we have so
far ONLY defined what we mean by greaterThan, lessThan, and difference. With
ONLY those definitions in place, we can define GCF:
gcf(a, b):
if a = b ---> a
if greaterThan(a, b) ---> gcf(difference(a, b), b)
if lessThan(a, b) ---> gcf(a, difference(b, a))
We can define gcf prior to defining division or mod. I think that's kind of
interesting. But certainly, outside the scope of this set of exercises, it
makes sense to use looping constructs, and Guido's gcf is pure beauty.
-----Original Message-----
From: kirby urner [mailto:[EMAIL PROTECTED]
Sent: Mon 02/19/07 10:05 PM
To: Michel Paul
Cc: [email protected]; Jane Wortman; Lee Morris
Subject: Re: [Edu-sig] understanding recursion
> The important thing in these exercises is that we can't use our typical
> arithmetic > operators of +, -, *, /, as we are DEFINING them!
I think a Pythoneer will twistedly think at this point is: why do you
say "can't use" we can can just *redefine* __add__, __sub__, other
__ribs__, to suit, get whatever meanings for those typical arithmetic
operators you like.
> And in the act of defining them, we naturally have to think recursively, as we
> haven't been given any looping constructs.
But in Python, we have been, given looping constructs (it's a VHLL ya know,
not an assembly language like Scheme and/or MMIX).
Kirby
_______________________________________________
Edu-sig mailing list
[email protected]
http://mail.python.org/mailman/listinfo/edu-sig
