Question

我有一个简单的程序可以进行多次转换，但在每次操作后都会跳出循环。在每个函数完成执行后，如何调整程序返回主循环。

#include <iostream>
#define TRUE 1

using namespace std;

int main(){

    char *str = new char[25];

    cout<< "What do you want to convert?" <<endl;
    cin>> str;

    while (TRUE){


        if (strcasecmp(str, "TEMPERATURE") == 0)
        {
            convert_temp(str);
        }
        if (strcasecmp(str, "WEIGHT") == 0)
        {
            convert_weight(str);
        }
        if (strcasecmp(str, "DISTANCE") == 0)
        {
            convert_distance(str);
        }

    }
    return EXIT_SUCCESS;
}

void convert_temp(char* str){

        cout<< "Press 1 for C to F | Press 2 for F to C" <<endl;
            int temp = 0;
            cin >> temp;
            if(temp == 1){
                int c, f = 0;
                cout<< "Enter the value" <<endl;
                cin >> c;
                f = (9/5)*c - 32;
                cout<< "The temperature is " << f << " degree F"<< endl;
            }else if (temp == 2){
                int c, f = 0;
                cout << "Enter the value"<<endl;
                cin >> f;
                c = (f-32)*(5/9);
                cout << "The temperature is " << c <<  " degree C"<<endl;
            }
            break;

}
void convert_weight(char* str){
    cout<< "Press 1 for POUNDS to KGS | Press 2 for KGS to POUNDS" <<endl;
            int temp = 0;
            cin >> temp;
            if(temp == 1){
                int k, p = 0;
                cout<< "Enter the value" <<endl;
                cin >> p;
                k = p/2.2046;
                cout<< "Your weight is " << k << " Kgs"<< endl;
            }else if (temp == 2){
                int k, p = 0;
                cout << "Enter the value"<<endl;
                cin >> k;
                p = k*2.2046;
                cout << "Your weight is " << p <<  " Pounds"<<endl;
            }
            break;
}

void convert_distance(char* str){
        cout<< "Press 1 for KM to MILES | Press 2 for MILES to KM" <<endl;
            int temp = 0;
            cin >> temp;
            if(temp == 1){
                int k, m = 0;
                cout<< "Enter the value" <<endl;
                cin >> k;
                m = 32*k;
                cout<< "The distance is " << k << " Miles"<< endl;
            }else if (temp == 2){
                int k, m = 0;
                cout << "Enter the value"<<endl;
                cin >> m;
                k = 10*m;
                cout << "The distance is " << k <<  " Kms"<<endl;
            }
            break;
}

因此，我的问题是如何通过调用main循环来替换break语句。我不希望在将所有这些函数插入主循环的序列中运行函数。

Answer 1

您的代码应该更像这样：

#include <iostream>
#include <string>

void convert_temp();
// Other prototypes elided

int main() {

    std::string str;

    for(;;) { // I use this in my coding standard to mean 'forever' instead of while(true)

        std::cout << "What do you want to convert?" << std::endl;
        std::cin >> str;

        if (str == "TEMPERATURE") {
            convert_temp();
        }
        if (str == "WEIGHT") {
            convert_weight();
        }
        if (str == "DISTANCE") {
            convert_distance();
        }
        if (str == "EXIT") {
            break;
        }
    }
    return 0;
}

void convert_temp() {

    std::cout << "Press 1 for C to F | Press 2 for F to C" << std::endl;
    int temp = 0;
    std::cin >> temp;
    std::cout << "Enter the value" << std::endl;
    int c, f = 0;
    if (temp == 1) {
        cin >> c;
        f = (9/5)*c - 32;
        std::cout << "The temperature is " << f << " degree F" << std::endl;
    } else if (temp == 2) {
        std::cin >> f;
        c = (f-32)*(5/9);
        std::cout << "The temperature is " << c <<  " degree C" << std::endl;
    }
}

// Other function definitions elided

请注意，作为C ++，我使用std::string作为主选择的输入。

main()函数现在循环询问'你想要转换什么？'每一次。

此参数不再传递给任何函数，因为它们知道它们在做什么，并且不需要使用该值。

示例convert_temp()函数已略有简化，break;已被删除，因为这在普通函数中没有任何作用。

另请注意输入'EXIT'如何退出程序。

Answer 2

您可以使用exit(0);退出整个程序。（无论如何，打破循环将导致关闭过程）

Answer 3

如果您希望继续使用主循环，则代码中不需要break语句。 Break means exit from the current control directive（for / switch）。您可以使用continue;替换break语句，但在这种情况下，这相当于没有continue语句。

将程序保持在主循环上

3 个答案: