simple calculator

def calculator(a, b, operator)
  if operator == "+"
    a + b
  elsif operator == "-"
    a - b
  elsif operator == "*"
    a * b
  elsif operator == "/"
    a / b
  else
    "unknown operator"
  end
end
    
calculator(1, 2, "+")
calculator(1, 2, "-")
calculator(1, 2, "*")
calculator(1, 2, "/")