Add index :: ReadForeign a => Number -> ForeignParser a

[philopon]

This PR allows parsing hetero list.

Please read examples/JSONHeteroArrays.purs file.

[garyb]

Thanks, index looks good 👍

I'm not totally convinced providing a default readTuple is the right thing to do as well, but I guess a 2-item JS array would be the most sensible default for this if we are going to provide one. What do you think @paf31?

I guess that can be overridden with a newtype elsewhere now if needed, so it's probably fine.

[paf31]

index looks good.

Is readTuple even used here? I'd prefer to keep it out of the core library if possible, especially without a newtype wrapper, since I don't think there is a single best default tuple instance. I feel like this sort of thing would be best kept in libraries.

Final call is yours though @garyb of course.

[garyb]

Yeah, that was pretty much what I was thinking.

@philopon can you update the PR to remove readTuple please.

[philopon]

Okay, I removed it. please check it.

[garyb]

Thanks!