Void SetGrade（int total）：[错误：无效使用void表达式]

Question

我有这样的代码：

#include <iostream>
using namespace std;
int main(){
    int total = 95;
    cout << "Grade is : " << SetGrade(total) << endl;
}
void SetGrade(int total){ 
     char Grade;
     if (total >= 90){
         Grade = 'A';
     }else if (total > 80 && total <= 89){
         Grade = 'B';
     }else if (total > 70 && total <= 79){
         Grade = 'C';
     }else if (total > 60 && total <= 69){
         Grade = 'D';
     }else{
         Grade = 'E';
     }
}

并且输出为：错误：无效使用void表达式。

Answer 1

您定义的函数将void作为返回类型。要将其传递给std :: cout，您需要传递一些东西。例如。像这样：

#include <iostream>
#include <string>

int main(){
    int total = 95;
    std::cout << "Grade is : " << total2Grade(total) << std::endl;
}
std::string total2Grade(int total){ 
     std::string Grade;
     if (total >= 90){
         Grade = 'A';
     }else if (total > 80 && total <= 89){
         Grade = 'B';
     }else if (total > 70 && total <= 79){
         Grade = 'C';
     }else if (total > 60 && total <= 69){
         Grade = 'D';
     }else{
         Grade = 'E';
     }
     return Grade;
}

Answer 2

Bro，这是用：]解决的>

#include <iostream>
using namespace std;
int main(){
    int total = 95;
    cout << "Grade is : "; SetGrade(total);
    return 0;
}
void SetGrade(int total){ 
     char Grade;
     if (total >= 90){
         Grade = 'A';
     }else if (total > 80 && total <= 89){
         Grade = 'B';
     }else if (total > 70 && total <= 79){
         Grade = 'C';
     }else if (total > 60 && total <= 69){
         Grade = 'D';
     }else{
         Grade = 'E';
     }
     cout << Grade;
}
感谢您对堆栈溢出做出贡献！