>> It sounds like you tried to redefine (>>) and
>> (>>=) and make 'do' use the new definitions.
>> This is not possible, regardless of what types
>> you give (>>) and (>>=).
>
> Watch out for rebindable syntax: (...)
>
> At first reading, I thought that
> -XNoImplicitPrelude was required to turn this
> on. But now I'm not sure: (...)
I wrote this test to check your sugestion. It does
build with -XNoImplicitPrelude, but not without
it:
----------
module Test where {
import Prelude hiding ( ( >> ) , ( >>= ) ) ;
data PseudoMonad a = PseudoMonad a ;
( >> ) = \(PseudoMonad x) (PseudoMonad _) -> PseudoMonad x ;
( >>= ) = (\(PseudoMonad a) f -> f a)
:: PseudoMonad Integer -> (Integer -> PseudoMonad Integer)
-> PseudoMonad Integer;
plusOne n = (PseudoMonad (n + 1))
:: PseudoMonad Integer;
c = (PseudoMonad 1) >> ((PseudoMonad 2) >>= (\n -> plusOne n));
d = do {(PseudoMonad 1) ; a <- (PseudoMonad 2) ; plusOne a }
}
----------
It's interesting that the types involved in >>=
etc. should still be like "t t1", that's why I had
to create PseudoMonad. Using just Integer (i.e., 2
>> 3 would be valid) doesn't work, even if all
operators are defined accordingly.
Best,
Maurício
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