Implement Data.Char (was: Module imports)

[geraldus]

I've unsuccessfully tried to import several modules (more precisely just a few functions from them), such as

• Control.Applicative
• Control.Monad
• even Data.Char

Is there a way to import any of them, of I have to reimplement needful functions (e.g. toUpper, mapM, unless, when, <*>, <$>)?

[bergmark]

Right, these haven't been added, probably because no one has asked for them before. There's a tradeoff here on whether we want to add separate modules for things or just stick as much as possible in Prelude. I have a branch of fay-base where I've split up everything in pretty much the same module hierarchy as GHC has. I'll need to check how much of a performance decrease it would be to have lots of modules in fay-base. I might also just wait until we get haskell-packages support since this wouldn't be an issue in that case.

For now we can add these to Prelude, so if you end up adding them please send a pull request! I don't think people will have overridden these identifiers to be anything else. Remember that <*> and <$> need to be monomorphic to Fay.

[geraldus]

@bergmark, Adam, so if I need to parse JavaScript String to, say, Haskell Double the solution is to declare foreign function, that takes care of it, instead of importing readS, what's impossible now. Right?

[bergmark]

Right. We should include that in fay-base too. This could be a module that isn't re-exported by Prelude so it wouldn't add any overhead when you aren't using it. It could contain any low level JS operations parseFloat/parseInt/setTimeout and others.

[geraldus]

@bergmark, Adam, I only described mapM with another name (e.g. 'f' stands for Fay), thus there is almost nothing to pull :)

fMapM :: (a -> Fay b) -> [a] -> Fay [b]
fMapM fn lst = sequence $ map fn lst

I have another question: surprisingly when works without any imports, but unless does not. If when exported to Fay, it would be great to have unless being exported as well!

[bergmark]

Data.Char is still up for grabs if anyone wants to implement it. For now I think it makes sense to let it import Prelude instead of the other way around for efficiency reasons.

As for <$> and <*>, I don't think they would be very useful to restrict them to Fay (or any other Functor/Applicative) so it's probably better for users to alias to these on their own when they need it.

[christianpbrink]

+1 on this being a need. I am not going to get around to implementing it myself, but it would be pretty nice to have.

[bergmark]

I added Data.Char, it contains ord and chr for now.

1a4dadba954c7a1254eed89919686137995a2dbf faylang/fay-base@eef4147f6316526e4f891aed9afe37d78633ebcd

[bergmark]

This has been in fay-base for a while now!