Christopher Done
Although, I'm pretty sure this use of tuples is inconsistent with what's in the Applicatives paper. It'd be:
[| (,) (g x y) (h (g x y))) |]
[| id f (g x y) (h [| (,) (g x y)) |] |]
I think that's the legit way to write it. The transformation is pretty trivial.
This has actually reminded me of another point. Tuples are one form of construction in Haskell that is somewhat special - but another is using record syntax. I wonder if it would be possible to use idiom brackets there to lift the record constructor too: (| T { a = x, b = y } |) This would desugar into (something like) (\a b -> T {..}) <$> x <*> y In this case, we've "lifted" the original syntax into the idiom brackets, so I think it's only natural that we're able to lift tuple construction into these brackets too. My preference would be that (| (g x y, h (g x y) |) Does the expected thing, where my expectation is (following on from my point about record syntax) would be: (\a b -> (a, b)) <$> g x y <*> h (g x y) -- Ollie