foldr function in Python

Marc 'BlackJack' Rintsch bj_666 at gmx.net
Fri Nov 23 10:31:06 CET 2007


On Fri, 23 Nov 2007 00:50:30 -0800, Ant wrote:

> So my point really is that foldr (perhaps renamed to make_reducer or
> something) could create idioms that are more readable than using
> reduce directly.

The name is definitely not so good because there is a `foldr` in Haskell
that just works like `reduce()`.  For partial applying you can use
``lambda`` or `functools.partial()`, unfortunately not with keyword
arguments as needed to set the initial value because `reduce()` just
accepts positional arguments.  So let's define `foldr()` in terms of
`reduce()`::

 foldr = lambda func, initial, iterable: reduce(func, iterable, initial)

 comma_separate = partial(foldr, insert_comma, '')

`insert_comma()` is left as an exercise for the reader.  :-)

I think that's better than a `make_reducer()`.

Of course it's a silly example because the "pythonic" way to define
`comma_separate()` is::

 comma_separate = ','.join

Ciao,
	Marc 'BlackJack' Rintsch



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