On Mon, Dec 10, 2012 at 7:23 PM, Takayuki Muranushi
Repeated thanks to you, Adam! Your code is brilliantly simple.
Sadly, I cannot reproduce the behaviors in your comments on my ghci (7.6.1) ..... Can we guess why? The version of packages we are using?
Mines are here.
https://github.com/nushio3/practice/tree/master/variable-arity/adam
:t forZ [1,2,3] (+) forZ [1,2,3] (+) :: (Num t, Num a, TypeCast br HFalse, HBuild2' br (HCons [t] HNil) (a -> a -> a) r) => r forZ [1,2,3] [10] (+)
<interactive>:13:1: Couldn't match type `[y]' with `(a0 -> a0 -> a0) -> t0' When using functional dependencies to combine Apply ApplyZap (a, b) [y], arising from the dependency `f a -> r' in the instance declaration at Part1.lhs:193:12 Apply ApplyZap ([[t2]], [t1]) ((a0 -> a0 -> a0) -> t0), arising from a use of `forZ' at <interactive>:13:1-4 In the expression: forZ [1, 2, 3] [10] (+) In an equation for `it': it = forZ [1, 2, 3] [10] (+)
forZ [1,2,3] "hi there" (,)
<interactive>:14:1: Couldn't match type `[y]' with `(a0 -> b0 -> (a0, b0)) -> t0' When using functional dependencies to combine Apply ApplyZap (a, b) [y], arising from the dependency `f a -> r' in the instance declaration at Part1.lhs:193:12 Apply ApplyZap ([[Char]], [t1]) ((a0 -> b0 -> (a0, b0)) -> t0), arising from a use of `forZ' at <interactive>:14:1-4 In the expression: forZ [1, 2, 3] "hi there" (,) In an equation for `it': it = forZ [1, 2, 3] "hi there" (,)
Best,
Takayuki
Hi Takayuki I must have changed the imports at some point: the file doesn't work here with the same HList and ghc versions either. It does work if I change the `import Data.HList.FakePrelude' to `import Data.HList.TypeCastGeneric2'. Finally another note is that it only simplifies the type for the first argument probably because of the hTrue in the definition of forZ: *P4> :t \x -> forZ [1,2,3] x (+) \x -> forZ [1,2,3] x (+) :: (Num a, Num t1, HBuild2' br (HCons [t1] HNil) b ((a -> a -> a) -> t), IsZip b br) => b -> t *P4> :t \x -> forZ x [1,2,3] (+) \x -> forZ x [1,2,3] (+) :: Num x => [x] -> [x] Adam