Stretching...

intro/slp.sml

@@ -0,0 +1,34 @@
+type id = string
+
+datatype binop = 
+	Plus 
+	| Minus
+	| Times
+	| Div
+
+datatype stm = 
+	CompoundStm of stm * stm 
+	| AssignStm of id * exp
+	| PrintStm of exp list
+and exp = IdExp of id
+	| NumExp of int
+	| OpExp of exp * binop * exp
+	| EseqExp of stm * exp
+
+val prog = CompoundStm (AssignStm ("a", OpExp (NumExp 5, Plus, NumExp 3)), 
+		CompoundStm (AssignStm ("b", EseqExp (PrintStm [IdExp "a", OpExp (IdExp "a", Minus, NumExp 1)], OpExp(NumExp 10, Plus, IdExp "a"))), PrintStm [IdExp "b"]))
+
+(* prog : stm *)
+
+(* Some exercises *)
+fun maxargs (s:stm) : int =
+    case s of 
+	CompoundStm (s1,s2) => Int.max (maxargs s1, maxargs s2)
+      | AssignStm (_,e) => (maxargs_expr e)
+      | PrintStm l => (List.length l)
+and maxargs_expr (e:exp) : int = 
+    case e of 
+	IdExp _ => 0
+      | NumExp _ => 0
+      | OpExp (e1,_,e2) => Int.max (maxargs_expr e1, maxargs_expr e2)
+      | EseqExp (s1,e1) => Int.max (maxargs s1, maxargs_expr e1)