1;2 + ((fn 2 => 99 | x => x) 3); let val x=99 in x+1 end; val rec fact = fn 0 => 1 | n => n * fact(n-1);fact 4; val rec append2 =  fn ([], ys) => ys   | (x::xs, ys) => x :: append2 (xs,ys);append2( [1,2,3], [4,5,6] ); val rec append =  fn xs => fn ys =>    case xs      of [] => ys       | x :: xs => x :: append xs ys;append [1,2,3] [4,5,6]; val reverse = fn xs =>  let    val rec loop = fn ([],ys) => ys                    | (x::xs,ys) => loop (xs,x::ys)  in    loop (xs, []) end;reverse [1,2,3,4];reverse [true,false]; val op @ = append2;infixr 5 @;[1,2,3] @ [4,5,6];