[Haskell-cafe] Funny State monad dependency
miguelimo38 at yandex.ru
Wed Apr 16 09:04:49 EDT 2008
It has nothing to do with State; it actually works in List monad.
"return y" is just another way of writing "[y]".
You don't need to import Control.Monad.State for this to work; you
only need Control.Monad (which is imported by the former).
On 16 Apr 2008, at 16:56, Hans Aberg wrote:
> When I load the State module in Hugs, then I can define the function
> f below, but I do not immediately see exactly what function "return"
> returns. Explanation welcome.
> For example:
> > f [2..4] [6..9]
> That is, it just repeats the second argument as many times as the
> length of the second argument.
> Hans Aberg
> import Control.Monad.State
> f :: Monad a => a b -> a c -> a c
> f x y = x >>= (return y)
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