On 21 Jun 2007, at 21:21, Bill Janssen wrote:
>>> It should amount to "map(+, operands)".
>>
>> Or, to be pedantic, this:
>>
>> reduce(lambda x, y: x.__add__(y), operands)
>
> Don't you mean:
>
> reduce(lambda x, y: x.__add__(y), operands[1:], operands[0])
In the absence of a "start" value reduce "does the right thing", so
you don't need to do that. My original post was asking for sum to
behave as Joel wrote. At the moment sum is more like:
def sum(operands, start=0):
return reduce(lambda x,y: x+y, operands, start)
Since the start value defaults to 0, if you don't specify a start
value and your items can't be added to zero you run into a problem.
I was proposing something that behaved more like:
def sum(operands, start=None):
if start is None:
operands , start = operands[1:], operands[0]
return reduce(lambda x,y: x+y, operands, start)
The best argument against this so far however is the one from Gareth
about what type is returned if no start value is given and the list
is also empty. Unless one is happy with the idea that sum([]) ==
None then I concede that the current behaviour is probably the best
compromise. That said, I still think that the special case rejection
of strings is ugly!
Cheers,
Nicko
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