c++ - 简单 C++ : How to globalise variables in C++

Question

当我尝试构建我的程序阅读时出现错误:'错误:'celsius()' 未在此范围内声明'

现在，如果我错了，请纠正我，但我认为问题在于，当我在华氏度函数中调用它时，函数“华氏度”出现在我的另一个函数“摄氏度”之前，它不会起作用。现在，切换它们就足够简单了，但是在摄氏度函数中也调用了华氏度。

在 python 中，您需要做的就是使用“全局”语法将其全局化，那么 C++ 的等价物是什么？

谢谢

附言。如果需要，这是我的代码。

#include <iostream>
#include <iomanip>
#include <cstdlib>
using namespace std;

int fahrenheit(){
    system("CLS");
    cout << "-----------------------------------------------";
    cout << "\nYOU HAVE CHOSEN FAHRENHEIT TO CELSIUS MODE";
    cout << "\n----------------------------------------------";
    bool again;
    again = true;
    while (again == true){
    int tempurf;
    cout << "\nFahrenheit Temperature to be Converted: ";
    cin >> tempurf;
    int tempurc;
    tempurc = tempurf - 32;
    tempurc = tempurc * 5;
    tempurc = tempurc / 9;
    cout << "\n\n" << tempurf << " F is " << tempurc << " C";
    cout << "\n\n\n\nWHAT WOULD YOU LIKE TO DO: ";
    cout << "\n      - ANOTHER CONVERSION TYPE A";
    cout << "\n      - FOR CELSIUS MODE TYPE C";
    cout << "\n      - TO EXIT TYPE E";
    bool goodc;
    goodc = false;
    while (goodc == false){
    string choosing;
    cout << "\n ";
    cin >> choosing;
    if (choosing == "A" or choosing == "a"){
        system("CLS");
        goodc = true;
    }
    else if (choosing == "C" or choosing == "c"){
        goodc = true;
        again = false;
        celsius();
    }
    else if (choosing == "E" or choosing == "e"){
        goodc = true;
        again = false;
        return 0;
    }
    else{
        cout << "\n Invalid Choice";
    }
    }
    }
}

int celsius(){
    system("CLS");
    cout << "---------------------------------------------";
    cout << "\nYOU HAVE CHOSEN CELSIUS TO FAHRENHEIT MODE";
    cout << "\n---------------------------------------------";
    bool again;
    again = true;
    while (again == true){
    int tempuc;
    cout << "\nCelsius Temperature to be Converted: ";
    cin >> tempuc;
    int tempuf;
    tempuf = tempuc * 9;
    tempuf = tempuf / 5;
    tempuf = tempuf + 32;
    cout << "\n\n" << tempuc << " C is " << tempuf << " F";
    cout << "\n\n\n\nWHAT WOULD YOU LIKE TO DO: ";
    cout << "\n      - ANOTHER CONVERSION TYPE A";
    cout << "\n      - FOR FAHRENHEIT MODE TYPE F";
    cout << "\n      - TO EXIT TYPE E";
    bool goodc;
    goodc = false;
    while (goodc == false){
    string choosing;
    cout << "\n ";
    cin >> choosing;
    if (choosing == "A" or choosing == "a"){
        system("CLS");
        goodc = true;
    }
    else if (choosing == "F" or choosing == "f"){
        goodc = true;
        again = false;
        fahrenheit();
    }
    else if (choosing == "E" or choosing == "e"){
        goodc = true;
        again = false;
        return 0;
    }
    else{
        cout << "\n Invalid Choice";
    }
    }
    }
}


int main(){
    cout << "Welcome to the Fahrenheit/Celsius Converter!";
    cout << "\n By Ben Sarachi";
    cout << "\n\nWhich way would you like to convert to:";
    cout << "\n      - If you would like Fahrenheit to Celsius please type F";
    cout << "\n      - If you would like Celsius to Fahrenheit please type C";
    // GC stands for good choice
    bool gc;
    gc = false;
    while (gc == false){
    string choice;
    cout << "\n   ";
    cin >> choice;
    //Call Functions
    if (choice == "F" or choice == "f"){
        gc = true;
        fahrenheit();
    }
    else if (choice == "C" or choice == "c"){
         gc = true;
         celsius();
    }
    else{
        cout << "Invalid Choice";
    }
    }
}

Answer 1

您想为您的函数添加前向声明，以便编译器知道该函数存在。发生的事情是华氏度调用摄氏度，但编译器此时不知道摄氏度是什么。

在您的代码顶部，将以下内容添加到您的包含项下方:

int fahrenheit();
int celsius();

这告诉编译器您将在某个时候定义这些函数。

然后您可以在文件中以您喜欢的任何顺序声明您的函数。

此外，为了将来引用，该前向声明应与您的函数具有相同的签名。所以如果你有这样的功能:

void foo(int bar) { ... }

那么您的前向声明将是:

void foo(int);