Lie Ryan wrote:
On 06/18/11 00:45, Franck Ditter wrote:
Hi, I'm just wondering about the complexity of some Python operations
to mimic Lisp car and cdr in Python...
def length(L) :
if not L : return 0
return 1 + length(L[1:])
Should I think of the slice L[1:] as (cdr L) ? I mean, is the slice
a copy of a segment of L, or do I actually get a pointer to something
inside L ? Is the above function length O(n) or probably O(n^2) ?
Where are such implementation things (well) said ?
Thanks,
franck
Your function does not mimic Lisp's car/cdr. This one does:
def car(L):
return L[0]
def cdr(L):
return L[1]
IANAL (I am not a Lisper), but shouldn't that be 'return L[1:]' ?
def length(L):
if not L: return 0
return 1 + length(cdr(L))
How is this different from regular ol' 'len' ?
~Ethan~
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