Malcolm Wallace wrote:
Wolfgang Jeltsch <[EMAIL PROTECTED]> writes:
I'm not sure exactly what you have in mind. Obviously I want something
that applies to all functions, with any number of arguments, and not
just (+). Furthermore, it should handle cases like 1+[2,3] where only
one value is monadic.
I doubt that it is a good thing to extend the language in a way that such
far reaching declarations are automatically generated.
I agree. The original request was for something like
[1,2] + [3,4]
to be automatically lifted into a monad. But surely it is not too
difficult to define the required behaviour precisely (and only)
where needed, e.g.
(+.) = liftM2 (+)
[1,2] +. [3,4]
Why not make the monad an instance of Num, then you do not proliferate
meaningless
similar symbols... besides which I am sure all the good ones are used in
libraries already
(like +. <+> etc) ;)
instance (Monad m, Show a) => Show (m a)
...
instance (Monad m, Ord a) => Ord (m a)
...
instance (Monad m, Num a,Show (m a),Ord (m a)) -> Num (m a) where
(+) = liftM2 (+)
The instances for Show and Ord can be empty if you don't need the
functionality...
Regards,
Keean.
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