On Mon, 2010-02-01 at 20:37 +0100, Hans Meine wrote:
> > >>> square = kaa.Callable(pow, 2)
> > >>> print square(5)
>
> In fact, this looks more like currying than like a partial function to me. ;-)
>
> (I.e. pow is curried, in the sense that arguments are 'attached'/'filled in'.)
>
> Although square will be a partial function in the sense that it cannot be
> called with arbitrarily typed objects, this is obviously not what is meant
> here.
I think currying is commonly mistaken for partial applications. I'd
also not properly understood the difference. It's possible I still
don't, mind you.
Currying is a functional construct, so I refer to [1] which defines
currying as:
Currying is the process of transforming a function that takes
multiple arguments into a function that takes just a single
argument and returns another function if any arguments are still
needed.
And according to [2] the partial application is:
Partial application in Haskell involves passing less than the
full number of arguments to a function that takes multiple
arguments.
I also like the definitions given in [3].
But basically currying of pow() would look like this:
>>> curry(pow)(2)(5)
32
Whereas the square() example in the docs is an example of a partial
application.
> However, I would have inserted 'even' into "They can [even] be used to
> construct...", or is this the only point of Callable objects?
Agreed, "even" is good suggestion. For kaa.Callable, it's really only
directly useful for partial applications, because otherwise you could
pass the underlying callable instead. But kaa.WeakCallable is useful in
the case of methods, even ignoring arguments.
Cheers,
Jason.
[1] http://www.haskell.org/haskellwiki/Currying
[2] http://www.haskell.org/haskellwiki/Partial_application
[3]
http://www.kirit.com/Blog:/2007-09-10/What%20do%20you%20get%20when%20you%20curry%20partial%20application%3F
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