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Add MFP (MonadFail proposal) #2

Open quchen opened 8 years ago

quchen commented 8 years ago

Straight adaption of the proposal as seen on the Trac Wiki, https://prime.haskell.org/wiki/Libraries/Proposals/MonadFail

Rendered version of this proposal: https://github.com/quchen/rfcs/blob/mfp/texts/0000-monadfail.rst

strake commented 8 years ago

I think we may want to wait here until we know what new type system features we will include; in particular, multi-parametre type classes would enable class MonadFail f m or some such.

quchen commented 8 years ago

When this standard is finished, MonadFail will have been in GHC for quite some time. I doubt we have much room for changes here. Early adopters already introduced MonadFail instances, we don’t want to break everything for yet another change in that department again.

cartazio commented 8 years ago

I think perhaps he's thinking of the isstring tweak for the either instance of monad fail that was recently proposed?

But yeah, any tweaks in that sphere should be well motivated by some experiments

On Sunday, August 21, 2016, David Luposchainsky notifications@github.com wrote:

When this standard is finished, MonadFail will have been in GHC for quite some time. I doubt we have much room for changes here. Early adopters already introduced MonadFail instances, we don’t want to break everything for yet another change in that department again.

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strake commented 8 years ago

@quchen: Nonetheless, i'd prefer to wait until we know our options to choose one.