haskell - How to generate arbitrary two argument function with QuickCheck? -

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i trying test implementation of zipwith using quickcheck. implementation, myzipwith, quickcheck test comparing standard function. like:

main =   quickcheck (prop_myzipwith :: (int -> int -> int) -> [int] -> [int] -> bool)  prop_myzipwith :: (a -> b -> c) -> [a] -> [b] -> bool prop_myzipwith f x y = (myzipwith x y) == (zipwith f x y)

this not work because (int -> int -> int) not instance of arbitrary.

with single-argument functions 1 can around using test.quickcheck.function's fun (which instantiates arbitrary). example:

main =   quickcheck (prop_mymap :: fun int int -> [int] -> bool)  prop_mymap :: fun b -> [a] -> bool prop_mymap (fun _ f) l = (mymap f l) == (map f l)

i trying similar except generating two-argument arbitrary functions.

how can generate arbitrary instances of 2 argument functions quickcheck testing of higher-order functions such zipwith?





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