pr6.spl

let postfixwithA:string = "a";;

let map (s:set f:string->string):set =
    (if (seteq s {}) then {}
    else (cons (f (head s)) (map (tail s) f)))
;;

let help (str:string):string =
    (strapp str postfixwithA)
;;

let union (first:set second:set):set = 
    (if (seteq first {}) 
    then (if (seteq second {}) then {} else (union second {}))
    else (cons (head first) (union (tail first) second)))
;;

let restrict (ins:set num:int):set = 
    (if (== num 0) then {}
    else (if (seteq ins {}) then {}
          else (cons (head ins) (restrict (tail ins) (- num 1)))))
;;

let setsUnion:set = (restrict (sort (union arg0 arg1)) maxoutput) in 
    (map setsUnion help);;