来源：

Question

所以我正在尝试返回int main中的边界和区域，但g++不断抛出错误消息。请帮助解释错误。感谢。

来源：

  1 // This program takes in two values and returns the perimeter and the area of the values taken.
  2 
  3 #include<iostream>
  4 using namespace std;
  5 
  6 double perimeter (double a, double b);
  7 double area (double a, double b);
  8 
  9 int main ()
 10 {
 11     // initialization
 12     double x, y, r, q;
 13 
 14     // inputs
 15     cout << "Please enter the first value (no units): " << endl;
 16     cin >> x;
 17     cout << "Please enter the second value (no units): " << endl;
 18     cin >> y;
 19 
 20     // perimeter
 21     cout << "The perimeter is: " << r << endl;
 22     r(x, y);
 23 
 24     // area
 25     cout << "The area is: " << q << endl;
 26     q(x, y);
 27     
 28     return 0;
 29 }   
 30 
 31 double perimeter (double a, double b)
 32 {
 33     2.0 * (a + b);
 34     return 0;
 35 }   
 36 
 37 double area (double a, double b)
 38 {
 39     a * b;
 40     return 0;
 41 }

输出：

x@xLinux:~$ g++ -Wall rectangle.cpp 
rectangle.cpp: In function ‘int main()’:
rectangle.cpp:22:11: error: ‘r’ cannot be used as a function
rectangle.cpp:26:11: error: ‘q’ cannot be used as a function
rectangle.cpp: In function ‘double perimeter(double, double)’:
rectangle.cpp:33:18: warning: statement has no effect
rectangle.cpp: In function ‘double area(double, double)’:
rectangle.cpp:39:10: warning: statement has no effect

Answer 1

因为您已将q和r定义为双打，所以您试图像对待() s

的函数一样“调用”它们

修改

此外，与其他答案一样，根据您要执行的操作，您需要将q和r定义为函数（就像您使用area和{ {1}}或者您需要在perimeter和x上调用您现有的两个函数，例如y

Answer 2

q和r被声明为double类型的变量。

您希望将perimeter(x,y)和area(x,y)用作：

// perimeter
cout << "The perimeter is: " << perimeter(x, y) << endl;

// area
cout << "The area is: " << area(x, y) << endl;

Answer 3

您已将q和r声明为变量。您不能将它们用作函数，因为它们不是函数。要使r(x,y)成为有效代码，您需要在某处double r(double x, double y) { ....}声明并删除r变量声明。

请阅读有关该语言基础知识的书籍或其他内容。

Answer 4

// This program takes in two values and returns the perimeter and the area of the values taken.

#include<iostream>
using namespace std;

double perimeter (double a, double b);
double area (double a, double b);

int main ()
{
     // initialization
     double x, y;

     // inputs
     cout << "Please enter the first value (no units): " << endl;
     cin >> x;
     cout << "Please enter the second value (no units): " << endl;
     cin >> y;

     // perimeter
     cout << "The perimeter is: " << perimeter(x, y) << endl;

     // area
     cout << "The area is: " << area(x, y) << endl;

     return 0;
 }   

 double perimeter (double a, double b)
 {
      return 2.0 * (a + b);
 }   

 double area (double a, double b)
 {
     return a * b;
 }

为什么'q'和'r'不能用作函数？

来源：

输出：

4 个答案: