map/filter/reduce/lambda opinions and background unscientific mini-survey

[Tom Anderson]

On Sun, 3 Jul 2005, Robert Kern wrote:

> Erik Max Francis wrote:
>> Ron Adam wrote:
>> 
>>> So you are saying that anything that has a 1% use case should be included 
>>> as a builtin function?
>>> 
>>> I think I can find a few hundred other functions in the library that are 
>>> used more than ten times as often as reduce.  Should those be builtins 
>>> too?
>>> 
>>> This is a practical over purity issue, so what are the practical reasons 
>>> for keeping it.  "It's already there" isn't a practical reason.  And it 
>>> covers 100% of it's own potential use cases, is circular logic without a 
>>> real underlying basis.
>> 
>> But the Python 3000 plan, at least what we've heard of it so far, isn't 
>> to move it to a standard library module.  It's to remove it altogether, 
>> replacing it with sum and product.  Since sum and product don't cover 
>> all the uses cases for reduce, this is a case of taking one function 
>> that handles all the required use cases and replacing it with _two_ 
>> functions that don't.  Since it's doubling the footprint of the reduce 
>> functionality, arguments about avoiding pollution are red herrings.
>
> Four, in fact. sum(), product(), any(), and all().

I'll just chip in and say i'd quite like a flatten(), too; at the moment, 
i have one like this:

def flatten(ll):
 	return reduce(lambda a, l: a.extend(l), ll, [])

A builtin, which had fast special-case code for then the argument is a 
list of lists (rather than an iterable of iterables), would be nice, since 
this is a reasonably big use of reduce for me.

How would one do that as a list comp, by the way? I'm really not very good 
with them yet.

> [1] Okay, there was that guy who predicted that list comprehensions and 
> first-class functions were the next to go. That was new. But also wrong. 
> I think we can discount that.

True. Guido will only get rid of those after he's got rid of lowercase 
letters in identifiers.

tom

-- 
A military-industrial illusion of democracy