Random functor monad

[imeckler]

I added functions

map : (a -> b) -> Generator a -> Generator b

and

andThen : Generator a -> (a -> Generator b) -> Generator b

to the Random module. Is there another name you prefer to andThen? I was shooting for consistency with the Maybe module. Also, does anyone have any ideas about a uniform convention for Applicative "instances"? Currently Random exports pair : Generator a -> Generator b -> Generator (a, b), but as far as I can tell no other module exports a function of the same name.

[kasbah]

+1 to merge this, I was looking for these and had started to write them myself.

[kasbah]

+1 to merge this, I was looking for these and had started to write them myself.

[kasbah]

Though I found your shadowing of generate a bit confusing. I had written this map:

map : (a -> b) -> Generator a -> Generator b
map f (Generator g) = Generator <| (\(v,seed) -> (f v, seed)) << g

and I changed your andThen to

andThen : Generator a -> (a -> Generator b) -> Generator b
andThen (Generator g) f = Generator <| \seed ->
    let (v,seed')     = g seed
        (Generator h) = f v
    in h seed'

for my own use.

[kasbah]

Though I found your shadowing of generate a bit confusing. I had written this map:

map : (a -> b) -> Generator a -> Generator b
map f (Generator g) = Generator <| (\(v,seed) -> (f v, seed)) << g

and I changed your andThen to

andThen : Generator a -> (a -> Generator b) -> Generator b
andThen (Generator g) f = Generator <| \seed ->
    let (v,seed')     = g seed
        (Generator h) = f v
    in h seed'

for my own use.

[evancz]

Thanks @imeckler, I think this will come in handy!

[evancz]

Thanks @imeckler, I think this will come in handy!