(* 目的：a, b, c を受け取ったら判別式の値を返す *) 
(* hanbetsushiki : float -> float -> float -> float *) 
let hanbetsushiki a b c = b *. b -. 4.0 *. a *. c 
 
(* テスト *) 
let test1 = hanbetsushiki 1.0 5.0 4.0 = 9.0 
let test2 = hanbetsushiki 2.0 (-4.0) 2.0 = 0.0 
let test3 = hanbetsushiki 1.0 2.0 4.0 = -12.0