2010/2/12 Andrey Fedorov :

Is that right, or am I missing something obvious?

The semantics are non-obvious, for one. I assume you mean that the following lines would be equivalent: starreduce(f, iterable, initial) reduce(lambda x,y: f(x, *y), iterable, initial) This is useful for the types of reduction where the result of the function is one type, and the iterable is a sequence of args to that function. For example: reduce(lambda x,y: str.replace(x, *y), (('a', 'aa'), ('b', 'bb',)), some_string) could be written as starreduce(str.replace, (('a', 'aa'), ('b', 'bb',)), some_string) It seems like a very narrow use-case, unless you mean something else. Vitor

Aside: there is no built-in for "lambda x, f: f(x)" somewhere, is there? On Fri, Feb 12, 2010 at 1:59 PM, Andrey Fedorov wrote:

On Fri, Feb 12, 2010 at 11:54 AM, Vitor Bosshard

...

wrote:

I assume you mean that the following lines would be equivalent:

...

starreduce(f, iterable, initial)

reduce(lambda x,y: f(x, *y), iterable, initial)

Precisely.

It seems like a very narrow use-case [...]

Agreed, that example is. I also use it for high-level functional stuff - something like Haskell's monads or Java's "chain-of-responsibility". Like:

output = reduce(lambda x, f: f(x), chain_of_processors, input)

So, given a list [f,g,h], this would be h(g(f(input))). The star-case is when input is a n-touple, and each function works on `n' arguments. But now that I wrote it out without a for loop, it's obviously trivial to add the star in the right place. My mistake! Thanks for helping me catch it :)

Cheers, Andrey

hah, I suppose I could do this with partial(apply, args=x), but that doesn't seem like the best idea. - Andrey On Fri, Feb 12, 2010 at 2:19 PM, Oleg Broytman wrote:

On Fri, Feb 12, 2010 at 01:59:45PM -0500, Andrey Fedorov wrote:

...

Aside: there is no built-in for "lambda x, f: f(x)" somewhere, is there?

apply(f, x) but why do you need it at all? Just call f(x).

Oleg. -- Oleg Broytman http://phd.pp.ru/ phd@phd.pp.ru Programmers don't die, they just GOSUB without RETURN. _______________________________________________ Python-ideas mailing list Python-ideas@python.org http://mail.python.org/mailman/listinfo/python-ideas