type complex = (f64,f64)

fun complexAdd((a,b): complex) ((c,d): complex): complex =
  (a + c,
   b + d)

fun complexMult((a,b): complex) ((c,d): complex): complex =
 (a*c - b * d,
  a*d + b * c)

fun complexInv((r,i): complex): complex =
  let denom = r*r + i * i
  in (r / denom,
      -i / denom)

fun complexNeg((r,i): complex): complex =
  (-r, -i)

fun complexConj((r,i): complex): complex =
  (r, -i)

fun main (o: int) (a: complex) (b: complex): complex =
  if      o == 0 then complexAdd a b
  else if o == 1 then complexMult a b
  else if o == 2 then complexInv a
  else if o == 3 then complexNeg a
  else                complexConj a