[Haskell-cafe] where versus let
Scott J.
jscott at skynet.be
Fri May 6 11:17:38 EDT 2005
Hi,
Instead of the following piece of code :
data State s a = S(s -> (a,s))
instance Monad (State s) where
return a = S(\s -> (a,s))
(S f ) >>= g = S(\s -> let (a,s1) = f s
S fun = g a
(b,s2) = fun s1
in (b,s2) )
I thought to write it in the following form using "where":
data State s a = S(s -> (a,s))
instance Monad (State s) where
return a = S(\s -> (a,s))
(S f ) >>= g = S(\s -> (b,s2)
where (a,s1) = f s
S fun = g a
(b,s2) = fun s1 )
However the compiler does not accept this use of "where". What is the reason?
Thanks
Jan
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