3.8

type Instruction = | ADD | SUB | MULT | DIV | SIN | COS | LOG | EXP | PUSH of float;;

type stack = List<float>

exception EmptyStack

let intpInstr (s:stack) (i:Instruction)  : stack =
    match (i, s) with
        | ADD, x :: y :: s'     ->  (x + y) :: s'
        | SUB, x :: y :: s'     ->  (x - y) :: s'
        | MULT, x :: y :: s'    ->  (x * y) :: s'
        | DIV, x :: y :: s'     ->  (x / y) :: s'
        | SIN, x :: s'          ->  sin (x) :: s'
        | COS, x :: s'          ->  cos (x) :: s'
        | LOG, x :: s'          ->  log (x) :: s'
        | EXP, x :: s'          ->  exp (x) :: s'
        | PUSH x, _             ->  x :: s
        | _                     ->  raise EmptyStack;;