Give MonadTrans a QuantifiedConstraints superclass

[Zemyla]

I feel like instead, MonadTrans should have a function

(>>==) :: Monad m => t m a -> (a -> t m b) -> t m b

That way, it can prove it's a Monad while still staying Haskell 98.

On Wed, Jun 2, 2021, 10:51 Viktor Dukhovni <ietf-dane at dukhovni.org> wrote:

> On Wed, Jun 02, 2021 at 07:27:28AM +0200, Henning Thielemann wrote:
>
> > So far, 'transformers' is mostly Haskell 98. This is why I prefer it
> > to 'mtl'. Wouldn't it be enough to add this extension to 'mtl'? I see
> > that 'mtl' re-uses the MonadTrans class from 'transformers' but maybe
> > it should define its own class with the quantified constraints then.
>
> I don't think that having two incompatible MonadTrans classes would
> constitute progress.  Older versions of the transformers library (which
> is by now quite stable) will continue to be available, for anyone who
> wants to use a Haskell '98 (ish?) version.
>
> [ FWIW, I don't know what you mean by "is mostly Haskell '98", I'd
>   expect that to be a strict binary choice: is or isn't. ]
>
> --
>     Viktor.
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