C为什么函数指针作为参数而不是一个函数？

问题描述

我一直在阅读有关函数作为参数的函数，特别是在C中，它们使用函数指针。假设我想实现牛顿raphson方法（以一种简单的方式）计算非线性方程中的零点。

  
参数 f 是派生和 newton_raphson 中的指针函数。
  double derivative（double f（double），double x）{...} 
  
完全等价于 
 
 
  double derivative（ double（* f）（double），double x）{...} 
  
只有前者看起来更好 - 通常当你可以省略括号时，你应该这样做。毕竟它们都相当于 
 
 
  double（（（（derivative）））（double（（（*（f） ）））（double（（trouble））），double（（x））））{...} 
  
我希望只能在IOCCC中使用。然而，如果你声明，定义一个变量（不是函数参数），你需要使用 
 
 
  double（* f）（double）; 
  
 as  
 
 
  double f（double）; 
  
仅仅是一个函数声明。 
 
 
 
 
 
  6.7.6.3函数声明符（包括原型） C11 draft n1570说： 
 
 
和
  6.9.1函数定义进一步说明那么 
 
 
另外它有以下例子：
 
I have been reading about having functions with functions as parameters, and particulary in C, they use function pointers. Let's suppose I want to implement the newton raphson method (in a simple way) for computing zeros in non linear equations.
double derivative(double f(double), double x)
{
    double h = 1e-9;
    return (f(x + h) - f(x)) / h;
}

double newton_raphson(double f(double), double x0, double tol)
{
    double xk, diff;

    do
    {
        xk = x0 - f(x0) / derivative(f, x0);
        diff = fabs(xk - x0);
        x0 = xk;
    } while (diff >= tol);
    return xk;
}
So, to compute an approximation for derivative I need a function that returns a double and takes a double as an argument. Same for computing a root of the function, given the other parameters. My question is, why is this different from declaring function parameters as function pointers? For instance declaring the input parameter f as a function pointer instead of just a function...
 解决方案 
The parameter f is a pointer-to-function in both derivative and newton_raphson.
double derivative(double f(double), double x) { ... }
is exactly equivalent to
double derivative(double (*f)(double), double x) { ... }
Only, the former looks nicer - usually when you can omit parentheses, you should probably do so. After all both of them are equivalent to
double ((((derivative)))(double (((*(f))))(double ((trouble))), double ((x)))) { ... }
That I hope will only ever be used in IOCCC.
However, if you're declaring, defining a variable (not a function parameter), you need to use
double (*f)(double);
as 
double f(double);
is just a function declaration.
6.7.6.3 Function declarators (including prototypes) of C11 draft n1570 says:
And6.9.1 Function definitions further says that
additionally it has the following example:
                        
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