使用函数作为另一个函数的输入

Question

嗨，我是很新的编码但我有一个相当复杂的pshysics问题CPP解决，我已经遇到了一些问题

#include <stdio.h> 
#include <cmath> 
#include <iostream> 

using namespace std; 

double delta_x(double x, double n) 
{ 
    return x/n; 
} 

double theta(delta_x(double x,double n),double i, double a) 
{ 
    return atan(abs(2*a*((delta_x(x,n)*i)-50)-(0.01))); 
} 

Codeblox Givex的我以下错误：

|9|error: expected primary-expression before 'double'| 
|9|error: expected primary-expression before 'double'| 
|9|error: expected primary-expression before 'double'| 
|9|error: expected primary-expression before 'double'| 
|9|error: expression list treated as compound expression in initializer [-fpermissive]| 
|10|error: expected ',' or ';' before '{' token| 
|20|error: 'theta' cannot be used as a function| 

在此先感谢

Answer 1

没有必要通过delta_x回theta：

double delta_x(double x, double n) 
{ 
    return x/n; 
} 

double theta(double i, double a) 
{ 
    return atan(abs(2*a*((delta_x(i,a)*i)-50)-(0.01))); 
}