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] [6,7,8,9,6,7,8,9,6,7,8,9] 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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