1 -- !!! ds005 -- mappairs from SLPJ Ch 5'
3 -- this simply tests a "typical" example
9 mappairs f (x:xs) [] = []
10 mappairs f (x:xs) (y:ys) = f x y : mappairs f xs ys
13 mappairs' f [] ys = []
15 mappairs' f (x:xs) (y:ys) = f x y : mappairs' f xs ys