foldr :: (a -> b -> b) -> b -> [a] -> b
foldr :: (b -> a -> a) -> a -> [b] -> a

are exactly the same types; simply inverted names for the type variables.

I don't clearly see any benefit.

Alex.

On Nov 12, 2015 12:00 PM, "Martin Vlk" <martin@vlkk.cz> wrote:

Hi, my first intuition about this is that in data constructor it
technically doesn't matter, but you could argue that "a" represents the
actual result of the function so it comes first.
Second comes the state, which is the side thing, hence the
secondary/less important position.

As for the order of type constructor parameters you are right - state is
part of the structure that Monoid, Functor, Applicative, Monad and the
like use.

Martin

martin:
> runState :: State s a -> s -> (a, s)
>
> I understand that in the constructor s has to be first, so we can turn (State s) into a monad. But why doesn't s come
> first in the result too, as in
>
> runState :: State s a -> s -> (s, a)
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