找不到标识符错误？

Question

我正在编写代码以使用 C++ 制作基于文本的基本二十一点游戏。我刚开始，但我立即运行遇到了一个问题。这是我到目前为止的代码，请注意，它并不意味着完整，甚至运行。是的，我知道它非常混乱和低效，我在我的第一个 C++ class 中。

我的问题是，每当我的代码调用任何递归函数（DealingHandler 和 EndProgram）时，我都会得到 "identifier not found"。是的，我知道有一个专门结束程序的功能在这个程序中是完全没有用的，但我不知道怎么突然结束程序没有这样的东西。

#include <iostream>
#include <string>
#include <cstdlib>
using namespace std; const int maxScore = 21; //immutable upper limit
                                              //string nameInput; - Idea for later.
int HandVal, DealerHandVal, Aceone, val, aceVal;
char HitStay;
string DealerHand, currenthand; //Strings to output the cards ( 4 5 for example)
int numAces, numTwo, numThree, numFour, numFive, numSix, numSeven, numEight, numNine, numTen, numJack, numQueen, numKing; //Inefficient way of making sure it doesn't give five twos out, however unlikely that may be.
int main() {
    cout << "Welcome to our C++ BlackJack Program." << endl;
    cout << "Please press enter to begin the game." << endl;
    system("PAUSE");//Bad.  Still easiest for a beginning C++ class.
    currenthand = "";
    numAces = 4;
    numTwo = 4;
    numThree = 4;
    numFour = 4;
    numFive = 4;
    numSix = 4;
    numSeven = 4;
    numEight = 4;
    numNine = 4;
    numTen = 4;
    numJack = 4;
    numQueen = 4;
    numKing = 4;
    int i = 2;
    {
        DealingHandler(i);
        cout << DealerHand;
        cout << "Press H to hit or S to stay." << endl;
        cin >> HitStay;
        switch (HitStay){
                    case 'H':
                        DealingHandler(1);
                        break;
                    case 'h':
                        DealingHandler(1);
                        break;
                    case 's':
                        EndProgram();
                        break;
                    case 'S':
                        EndProgram();
                        break;
                    default:
                        cout << "Invalid entry.";
                        break;
        }
    }
    system("PAUSE");
}
int DealingHandler(int HowManyDealed) {
    for (int x = 0; x <= HowManyDealed; x++) {
        val = rand() % 13;
        switch (val) {
        case '1':
            cout << "A";
            cout << "Press One to set this Ace equal to one.  Press Two to set it equal to eleven.  This cannot be changed, so choose wisely!" << endl;
            cin >> aceVal;
            if (aceVal = 1) {
                Aceone = 1;
                currenthand += " 1";
                cout << currenthand << endl;
                HandVal += 1;
            }
            if (aceVal = 2) {
                Aceone = 11;
                currenthand += " 11";
                cout << currenthand << endl;
                HandVal += 11;
            }
            numAces = numAces - 1;
        case '2':
            currenthand += " 2";
            cout << currenthand << endl;
            HandVal += 3;
            numTwo -= 1;
            break;
        case '3':
            currenthand += " 3";
            cout << currenthand << endl;
            HandVal += 3;
            numThree -= 1;
            break;
        case '4':
            currenthand += " 4";
            cout << currenthand << endl;
            HandVal += 4;
            numFour -= 1;
            break;
        case '5':
            currenthand += " 5";
            cout << currenthand << endl;
            HandVal += 5;
            numFive -= 1;
            break;
        case '6':
            currenthand += " 6";
            cout << currenthand << endl;
            HandVal += 6;
            numSix -= 1;
            break;
        case '7':
            currenthand += " 7";
            cout << currenthand << endl;
            HandVal += 7;
            numSeven -= 1;
            break;
        case '8':
            currenthand += " 8";
            cout << currenthand << endl;
            HandVal += 8;
            numEight -= 1;
            break;
        case '9':
            currenthand += " 9";
            cout << currenthand << endl;
            HandVal += 9;
            numNine -= 1;
            break;
        case '10':
            currenthand += " 10";
            cout << currenthand << endl;
            HandVal += 10;
            numTen -= 1;
            break;
        case '11':
            currenthand += " J";
            cout << currenthand << endl;
            HandVal += 10;
            numJack -= 1;
            break;
        case '12':
            currenthand += " Q";
            cout << currenthand << endl;
            HandVal += 10;
            numQueen -= 1;
            break;
        case '13':
            currenthand += " K";
            cout << currenthand << endl;
            HandVal += 10;
            numKing -= 1;
            break;
        }
        if (HandVal < 21) {
            cout << "Busted!" << endl;
            EndProgram();
        }

    }
    return HandVal;
}
void EndProgram()
        {
            cout << "I hope you had fun with my game!";
            system("PAUSE");
        }

在此先感谢您对我的帮助。

Answer 1

This 是声明、原型和定义的一个很好的例子，这些都是您需要知道的。

函数原型是一种声明函数结构体的方法，例如：

int my_function(int arg1, int arg2);

事实上，在函数原型中你甚至不需要输入参数名称，只需要输入它们的类型：

int my_function(int, int);

随着编译过程从上到下，当你有这段代码时

// function a definition
int function_a()
{
    int some_variable = function_b();
}

// function b definition
int function_b()
{
    return 20;
}

当您在 function_a() 中调用编译器时，编译器将对 function_b() 一无所知，因此，您必须像这样重新排序代码

// function b definition
int function_b()
{
    return 20;
}

// function a definition
int function_a()
{
    // now the compiler knows how function_b() works, or, at least, what arguments she need
    int some_variable = function_b();
}

或使用原型来保留您的代码组织，就像这样

// function b prototype
int function_b();

// function a definition
int function_a()
{
    int some_variable = function_b();
}

// function b definition
int function_b()
{
    return 20;
}

所以，现在，编译器知道存在一个 "function_b"，并且知道她的参数和 return 值类型是什么（在这种情况下，没有参数和 return 类型是 int)

为了顺序，您通常会将函数原型放在头文件（.h）中，将定义放在代码文件中（.c/cpp）

在您的示例中，您在主函数内部调用了 DealingHandler 和 EndProgram 函数，但它们是稍后定义的，这就是您收到错误的原因。所以，使用函数原型你可以很容易地修复它，把

/* this can be
int DealingHandler(int);
because function prototypes doesn't need argument's name, just their types */
int DealingHandler(int HowManyDealed);
void EndProgram();

在 main() 函数上，或者更好的是，在这一行下面

using namespace std;

找不到标识符错误？

Identifier not found error?

c++

identifier