哈斯克爾 - 傳遞一個函數作爲參數

Question

所以在Haskell我有以下問題提出了兩個功能（他們只是執行一些數學運算）

cubicQ :: Float -> Float -> Float -> Float 
cubicQ a b c = (3*a*c - b**2)/(9*a**2) 

cubicR :: Float -> Float -> Float -> Float -> Float 
cubicR a b c d = (9*a*b*c - 27*(a**2)*d-2*b**3) 

我做第三函數生成立方體有一個要求，即該函數的類型爲Float - > Float - > Float，它計算q和r的輸出，它是cubicQ和cubicR的輸出。如何將函數cubicQ和cubicR作爲參數q和r以立方體的形式傳遞？以下是我到目前爲止所嘗試的，但我很難過。任何幫助將不勝感激。

cubicS q r = (r+ (q**3+r**2)**(1/2))**(1/3) 
    where q = (cubicQ a b c d) 
      r = (cubicR a b c) 

Answer 1

試試這個：

cubicQ a b c = (3*a*c - b**2)/(9*a**2) 
cubicR a b c d = (9*a*b*c - 27*(a**2)*d-2*b**3) 
cubicS q r = (r+ (q**3+r**2)**(1/2))**(1/3) 

f a b c d = cubicS (cubicQ a b c) (cubicR a b c d) 

main = do print $ f 1 2 3 4 

---

或：

cubicS a b c d = (r+ (q**3+r**2)**(1/2))**(1/3) 
    where q = cubicQ a b c 
     r = cubicR a b c d 

---

或：

cubicS a b c d = 
    let q = cubicQ a b c 
     r = cubicR a b c d 
    in (r+ (q**3+r**2)**(1/2))**(1/3) 

看到：

cubicQ :: Float -> Float -> Float -> Float 
cubicQ a b c = (3*a*c - b**2)/(9*a**2) 

cubicR :: Float -> Float -> Float -> Float -> Float 
cubicR a b c d = (9*a*b*c - 27*(a**2)*d-2*b**3) 

cubicS :: Float -> Float -> Float -> Float -> Float 
cubicS a b c d = 
    let q = cubicQ a b c 
     r = cubicR a b c d 
    in 
    (r+ (q**3+r**2)**(1/2))**(1/3) 

main = do print $ cubicS 1.1 2.2 3.3 4.4 

輸出：

9.736999e-2 

---

，如果你限制在cubicS是cubicS: Float -> Float -> Float：

cubicQ a b c = (3*a*c - b**2)/(9*a**2) 
cubicR a b c d = (9*a*b*c - 27*(a**2)*d-2*b**3) 
cubicS q r = (r+ (q**3+r**2)**(1/2))**(1/3) 

cureS a b c d = cubicS q r 
    where q = cubicQ a b c 
      r = cubicR a b c d 

main = do print $ cureS 1.1 2.2 3.3 4.4