From: Brian Mitchell <binary42@...>
Date: 2006-04-21T07:31:37+09:00
Subject: Re: Converting IP range to array of IP's

On 4/20/06, Tom Moertel <tom@moertel.com> wrote:
> Brian Mitchell wrote:
> > Other's solutions should work great but just for fun and enlightenment
> > I wrote my own little implementation of a simple list comprehension in
> > Haskell ....
>
> You might also find fun in what 'sequence' does in the List monad:
>
>      Prelude> :t sequence
>      sequence :: (Monad m) => [m a] -> m [a]
>
>      Prelude> mapM_ print $ sequence [[192], [168], [0,1], [1..10]]
>      [192,168,0,1]
>      [192,168,0,2]
>      [192,168,0,3]
>      [192,168,0,4]
>      [192,168,0,5]
>      [192,168,0,6]
>      [192,168,0,7]
>      [192,168,0,8]
>      [192,168,0,9]
>      [192,168,0,10]
>      [192,168,1,1]
>      [192,168,1,2]
>      [192,168,1,3]
>      [192,168,1,4]
>      [192,168,1,5]
>      [192,168,1,6]
>      [192,168,1,7]
>      [192,168,1,8]
>      [192,168,1,9]
>      [192,168,1,10]


Thanks. I was already aware of that but didn't think of naming my
example method that name. Good to have that pointed out to me every
once in a while (for some reason I have not gotten used to using
monadic functions on lists yet).

After writing this I think it might be fun to write a monadic
extension library and maybe add a collection of monad transformers.
This would bring a very powerful set of tools to Ruby. Maybe someone
can come up with some nice DSL like Haskell's do notation. I haven't
found one yet.

Brian.