return-statement-in-c-cpp-with-examples.md

C/c++ 中的返回语句，示例

原文:https://www . geesforgeks . org/return-statement-in-c-CPP-with-examples/

先决条件: 在 C/C++ 中的功能

返回语句将执行流程返回到函数，从这里调用它。这个语句不一定需要任何条件语句。语句一执行，程序的流程立即停止并从调用它的地方返回控制。return 语句可以为 void 函数返回任何东西，也可以不返回任何东西，但是对于非 void 函数，必须返回一个返回值。

语法:

return[expression];

使用返回语句的方式有多种。下面提到的很少:

1. **不返回值的方法:**在 C/C++ 中，当方法属于返回类型时，不能跳过返回语句。仅对于 void 类型，可以跳过 return 语句。

   • Not using return statement in void return type function: When a function does not return anything, the void return type is used. So if there is a void return type in the function definition, then there will be no return statement inside that function (generally).

     语法:

     void func()
     {
         .
         .
         .
     }
     

     例:

     C

     // C code to show not using return
     // statement in void return type function
     
     #include <stdio.h>
     
     // void method
     void Print()
     {
         printf("Welcome to GeeksforGeeks");
     }
     
     // Driver method
     int main()
     {
     
         // Calling print
         Print();
     
         return 0;
     }

     C++

     // C++ code to show not using return
     // statement in void return type function
     
     #include <iostream>
     using namespace std;
     
     // void method
     void Print()
     {
         printf("Welcome to GeeksforGeeks");
     }
     
     // Driver method
     int main()
     {
     
         // Calling print
         Print();
     
         return 0;
     }

     Output:

     Welcome to GeeksforGeeks
     

   • Using return statement in void return type function: Now the question arises, what if there is a return statement inside a void return type function? Since we know that, if there is a void return type in the function definition, then there will be no return statement inside that function. But if there is a return statement inside it, then also there will be no problem if the syntax of it will be:

     正确语法:

     void func()
     {
         return;
     }
     

     该语法在函数中用作跳转语句，目的是中断函数的流程并跳出它。人们可以把它看作是在函数中使用的“ break 语句”的替代。

     例:

     C

     // C code to show using return
     // statement in void return type function
     
     #include <stdio.h>
     
     // void method
     void Print()
     {
         printf("Welcome to GeeksforGeeks");
     
         // void method using the return statement
         return;
     }
     
     // Driver method
     int main()
     {
     
         // Calling print
         Print();
         return 0;
     }

     C++

     // C++ code to show using return
     // statement in void return type function
     
     #include <iostream>
     using namespace std;
     
     // void method
     void Print()
     {
         printf("Welcome to GeeksforGeeks");
     
         // void method using the return statement
         return;
     }
     
     // Driver method
     int main()
     {
     
         // Calling print
         Print();
         return 0;
     }

     Output:

     Welcome to GeeksforGeeks
     

     但是如果 return 语句试图在 void 返回类型函数中返回一个值，这将导致错误。

     语法错误:

     void func()
     {
         return value;
     }
     

     警告:

     warning: 'return' with a value, in function returning void
     

     例:

     C

     // C code to show using return statement
     // with a value in void return type function
     
     #include <stdio.h>
     
     // void method
     void Print()
     {
         printf("Welcome to GeeksforGeeks");
     
         // void method using the return
         // statement to return a value
         return 10;
     }
     
     // Driver method
     int main()
     {
     
         // Calling print
         Print();
         return 0;
     }

     C++

     // C++ code to show using return statement
     // with a value in void return type function
     
     #include <iostream>
     using namespace std;
     
     // void method
     void Print()
     {
         printf("Welcome to GeeksforGeeks");
     
         // void method using the return
         // statement to return a value
         return 10;
     }
     
     // Driver method
     int main()
     {
     
         // Calling print
         Print();
     
         return 0;
     }

     Warnings:

     prog.c: In function 'Print':
     prog.c:12:9: warning: 'return' with a value, in function returning void
       return 10;
              ^
     

2. Methods returning a value: For methods that define a return type, the return statement must be immediately followed by the return value of that specified return type.

   语法:

   return-type func()
   {
       return value;
   }
   

   例:

   C

   // C code to illustrate Methods returning
   // a value using return statement
   
   #include <stdio.h>
   
   // non-void return type
   // function to calculate sum
   int SUM(int a, int b)
   {
       int s1 = a + b;
   
       // method using the return
       // statement to return a value
       return s1;
   }
   
   // Driver method
   int main()
   {
       int num1 = 10;
       int num2 = 10;
       int sum_of = SUM(num1, num2);
       printf("The sum is %d", sum_of);
       return 0;
   }

   C++

   // C++ code to illustrate Methods returning
   // a value using return statement
   
   #include <iostream>
   using namespace std;
   
   // non-void return type
   // function to calculate sum
   int SUM(int a, int b)
   {
       int s1 = a + b;
   
       // method using the return
       // statement to return a value
       return s1;
   }
   
   // Driver method
   int main()
   {
       int num1 = 10;
       int num2 = 10;
       int sum_of = SUM(num1, num2);
       cout << "The sum is " << sum_of;
       return 0;
   }

   Output:

   The sum is 20