(*
 * expr.sml
 * cs334
 *)

(* Magic constant to make datatypes print out fully *)
Control.Print.printDepth:= 100;
Control.Print.printLength:= 100;

datatype Expr = 
    VarX
  | VarY
  | Sine     of Expr
  | Cosine   of Expr
  | Average  of Expr * Expr
  | Times    of Expr * Expr;       


(* build functions:
     Use these helper functions to generate elements of the Expr
     datatype rather than using the constructors directly.  This
     provides a little more modularity in the design of your program
*)
fun buildX()             = VarX;
fun buildY()             = VarY;
fun buildSine(e)         = Sine(e);
fun buildCosine(e)       = Cosine(e);
fun buildAverage(e1,e2)  = Average(e1,e2);
fun buildTimes(e1,e2)    = Times(e1,e2);


(* exprToString : Expr -> string
   Complete this function to convert an Expr to a string 
*)
fun exprToString e = "not written";    
    
(* eval : Expr -> real*real -> real
   Evaluator for expressions in x and y
 *)
fun eval e (x,y) = 0.0;
	
val sampleExpr =
      buildCosine(buildSine(buildTimes(buildCosine(buildAverage(buildCosine(
      buildX()),buildTimes(buildCosine (buildCosine (buildAverage
      (buildTimes (buildY(),buildY()),buildCosine (buildX())))),
      buildCosine (buildTimes (buildSine (buildCosine
      (buildY())),buildAverage (buildSine (buildX()), buildTimes
      (buildX(),buildX()))))))),buildY())));

(************** Add Testing Code Here ***************)