signature MATH =
   sig
      type real

      val acos: real -> real 
      val asin: real -> real 
      val atan2: real * real -> real 
      val atan: real -> real 
      val cos: real -> real 
      val cosh: real -> real 
      val e: real
      val exp: real -> real 
      val ln: real -> real 
      val log10: real -> real 
      val pi: real 
      val pow: real * real -> real 
      val sin: real -> real 
      val sinh: real -> real 
      val sqrt: real -> real 
      val tan: real -> real 
      val tanh: real -> real 
   end
