[Haskell-cafe] 'Associative' order of calling
Charles Durham
ratzes at gmail.com
Fri Oct 23 15:45:13 UTC 2015
Yeah, sorry, should have provided an example to begin with.
Let's say you have a function "thisFold :: (a -> a -> a) -> [a] -> a"
and it says that the function 'f' passed in must be associative.
Then it goes on to use f in "thisFold f [0,1,2]" like "f (1 (f 0 2))".
Obviously f is still associative, but 'thisFold' did not call f
'associatively' on the data. My question is if there is a name for what
property this broke by not calling f 'associatively'.
Does that make sense?
On Fri, Oct 23, 2015 at 11:21 AM, Francesco Ariis <fa-ml at ariis.it> wrote:
> On Fri, Oct 23, 2015 at 10:26:08AM -0400, Charles Durham wrote:
> > Is there a name for a fold that promises to call a function such that
> only
> > an associative function will always return the same result. Or in other
> > words, it has the property that it promises to call a function
> > "associatively" on a set of data?
>
> I am not sure I am understanding the question correctly. Every Monoid has a
> single binary operation which happens to be associative and one of
> the basic fold functions has signature
>
> foldMap :: (Foldable t, Monoid m) => (a -> m) -> t a -> m
>
> (which does what you expect). Does that answer your question? If not,
> I'd be grateful if you would provide an example.
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