Probably needs to use fold-left and map function. I also think this needs to use append function. This should be implemented in lambda calculus with scheme.

Define a function removeDup, which takes a list of ordered numbers, and returns a list that is identical to the input except that duplicated numbers are removed. For example, (removeDup '(1 1 2)) should return (1 2); (removeDup '(35 57779)) should return (3 5 7 9)