Production code: a division that throws on a zero divisor

#!ek9
defines module site.testing.assertions

  defines function

    checkedDivide() as pure
      ->
        dividend as Integer
        divisor as Integer
      <- quotient as Integer?

      //Integer division by zero does not throw: it gives an unset Integer.
      //So a function that must fail says so explicitly.
      if divisor == 0
        throw Exception("division by zero")
      quotient: dividend / divisor