CSE 428, Spring 2000: Solution of Assignment #8

   fun curry f x y = f(x,y);

   fun curry f = fn x => fn y => f(x,y);
   val curry = fn f => fn x => fn y => f(x,y);

   fun filter p [] = []
     | filter p (x::l) = (if p x then [x] else []) @ filter p l;

1.    val length = let fun plus1(x,y) = 1 + y 
                    in reduce plus1 0
                   end;
   

   or, equivalently:

      val length = reduce (fn(x,y) => 1 + y) 0;
   

2.    val maximum_positive = let fun max(x,y) = if x>y then x else y
                              in reduce max 0
                             end;
   

   or, equivalently:

      val maximum_positive = reduce (fn(x,y) => if x>y then x else y) 0;
   

3.    val reverse = let fun insert_at_end (x,l) = l @ [x]
                     in reduce insert_at_end  []
                    end;
   

   or, equivalently:

      val reverse = reduce (fn(x,l) => l @ [x]) false;
   

4.    fun occurs x = let fun found (y,b) = b orelse x=y
                      in reduce found false
                     end;
   

   or, equivalently:

      fun occurs x = reduce (fn(y,b) => b orelse x=y) false;
   

1.    val f = fn x => fn y => (x,y);
   

   or equivalently:

      fun f x y = (x,y);
   

2.    val g = fn u => fn x => u(x,x);
   

   or equivalently:

      fun g u x = u(x,x);
   

3.    val h = fn u => fn l => [u(hd l)];
   

   or equivalently:

      fun h u l = [u(hd l)];