On Mon, 2 May 2011 06:49:41 +1000, Chris Angelico
<ros...@gmail.com> wrote:
: Sure. Serialize this Python object in a way that can be given to, say, PHP:
: foo={"asdf":"qwer","zxcv":"1234"}; foo["self"]=[1,2,3,foo]
: Recurse from self into the list, recurse from there into a
: dictionary... Okay, that's a rather naive recursion and fraught with
: risk, but there are more complex examples. And watching for cyclic
: references would be O(N*N) as you'd need to maintain a full list of
: every PyObject* that you've sighted (talking here from the C API, but
: the same consideration applies whichever way you do it).
Wouldn't cyclic references give infinite recursion? And remain
infinitive if you recode it iteratively?
: I'm not sure that recursion is clearer. Recursion is a way of
: expressing the two rules:
:
: 1! = 1
: n! = n * (n-1)!
:
: But iteration is a way of expressing this equivalent rule:
:
: n! = 1 * 2 * 3 * ... * n-1 * n
:
: It really depends what you're trying to say.
True. There is a place for everything. However, in the example
above, you can map the recursive definition directly into python
without further ado. In order to express the one-liner in python,
as iteration, you need to introduce additional elements, namely
a state (index variable). Hence, recursion is clearer by being
close to the language you would normally use to describe the
problem.
--
:-- Hans Georg
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