[Haskell-cafe] Re: Grokking monads by not overlooking concatMap

[Peter Hercek]

Achim Schneider wrote:
> -- That's the one I've been looking for. Remember that
> -- return e = [e]
> f'''' = concatMap 
>         (\x -> concatMap 
>             (\y -> concatMap 
>                 (\_ -> [(x,y)])
>                 (if x*y == 8 then [()] else []))
>             [2..8])
>         [1..4]
> 
> Morale: Premature term elimination is the root of all misunderstanding.
> 
> Haskell wins the wickedness of design contest by using [()] and [] as
> truth values.

Maybe you wanted to say: "... by using [()] as True value and [] as
  False value" ... which does not seem that wicked (at least to me).

Peter.