1val x = 0 2 3val hello = "hello world" 4 5val id = fn x => x 6 7fun id' x = x 8 9val () = print "hello world\n" 10 11val _ = let 12 val hello = "hello" 13 val world = "world" 14in 15 print (hello ^ " " ^ world ^ "\n") 16end 17 18fun isZero n = 19 if n = 0 then true 20 else false 21 22fun isTrue b = 23 case b of 24 true => true 25 | false => false 26 27exception Bad_value of string 28 29fun isTrue' b = 30 case b of 31 true => true 32 | _ => raise (Bad_value "value is not true!") 33 34val alwaysTrue = 35 isTrue' false handle Bad_value _ => true 36 37datatype myBool = True | False 38 39datatype shape = Square of real | Circle of real | Point 40 41signature FOO = sig 42 val foo : 'a -> 'a 43end 44 45structure Foo :> FOO = struct 46 fun foo x = x 47end 48