Question

嗨伙计们（和女孩们），我在使用Python太长时间之后，正在努力重新熟悉C ++。我已经用MS Visual C ++ 2010 Express版编写了一个小程序，我已经找到了一个罪魁祸首，为什么编译器似乎不喜欢我使用枚举类Choice。编译器抱怨不存在具有此名称的命名空间。现在，我应该说我之前编写的所有C / C ++代码都是在学术环境中，因此我使用的是完整的IDE。无论如何，我附上下面的代码，请原谅我，如果这是不正确的方法发布它。如果是，请参考我正确的方法，我将从此采用它。提前感谢您提供任何可能借出的帮助或见解。代码如下。

#include"stdafx.h"
#include<iostream>
#include<string>
#include<ctime>
using namespace std;

enum class Choice { rock, paper, scissors };
using namespace Choice;**

Choice player_choice;    //holds user's move
Choice machine_choice;   //holds machine's move

string words[3] = {"rock","paper","scissors"};

Choice get_machine_choice();
void decide_winner();
string get_msg(Choice winner);
int rand0toN1(int n);
int main(int argc, char *argv[])
{
    srand(time(NULL));    //set randomization
    string input_str;
    int c;
    while (true) {
        cout << "Enter Rock, Paper, Scissors, or Exit: ";
        getline(cin, input_str);
        if (input_str.size() < 1) {
            cout << "Sorry, I don't understand that.\n";
            continue;
        }
        c = input_str[0];
        if (c == 'R' || c == 'r')
            player_choice = rock;
        else if (c == 'P' || c == 'p')
            player_choice = paper;
        else if (c == 'S' || c == 's')
            player_choice = scissors;
        else if (c == 'E' || c == 'e')
            break;
        else {
            cout << "Sorry, I don't understand that.\n";
            continue;
        }
        machine_choice = get_machine_choice();
        int p = (int) player_choice;
        int c = (int) machine_choice;
        cout << "You Choose " << words [p];
        cout << "," << endl;
        cout << "I choose " << words [c];
        cout << "," << endl;
        decide_winner();
    }
    return EXIT_SUCCESS;
}

Choice get_machine_choice() {
    int n = rand0toN1(3);
    if (n == 0) return rock;
    if (n == 1) return paper;
    return scissors;
}

void decide_winner() {
    if (player_choice == machine_choice) {
        cout << "Reult is a tie.\n\n";
        return;
    }
    int p = static_cast<int>(player_choice);
    int c = static_cast<int>(machine_choice);
    if (p - c == 1 || p - c == -2) {
        cout << get_msg(player_choice);
        cout << "Unfortunantly, you win...\n";
    } else {
        cout << get_msg(machine_choice);
        cout << "I WIN, BEEEATCH!!!!\n";
    }
    cout << endl;
}

string get_msg(Choice winner) {
    if (winner == rock)
        return string("Rock smashes scissors, beeatch...");
    else if (winner == paper)
        return string("You know what paper does to rock, COVERAGE!!...");
    else
        return string("CHOP! Scissors cut paper!!....");
}

int rand0toN1(int n) {
    return rand() % n;
}

再次感谢您抽出宝贵时间帮助我。我似乎记得经常使用C ++声明类，并且无法弄清楚它为什么不能识别它。再次感谢您抽出宝贵时间。法院（克莱姆森大学，SC）

Answer 1

VC ++在2010年不支持enum类。您需要2012。

Answer 2

visual c ++ 2010不支持

enum class，但我认为它在vc ++ 2012中。见here。

您必须升级编译器或使用简单的“枚举”，当然这种方法稍有不同。

Answer 3

所以看起来你想要使用命名空间“Choice”，但你没有先定义它。要定义新的命名空间，请按以下方式对其进行定义：

namespace X { // namespace definition
  int a;
  int b;
  }
using namespace X; //then you can use it

但事实上，我不确定你是否需要定义任何名称空间...... 在您的情况下，我确定的问题是您声明“枚举类选择”，而不是简单地“枚举选择”。请阅读以下关于c ++中枚举用法的链接：http://www.cplusplus.com/forum/beginner/44859/

我以这种方式修改了代码，运行正常：

#include"stdafx.h"
#include<iostream>
#include<string>
#include<ctime>
using namespace std;

enum Choice { 
        rock, 
        paper, 
        scissors };

Choice player_choice;    //holds user's move
Choice machine_choice;   //holds machine's move

string words[3] = {"rock","paper","scissors"};

Choice get_machine_choice();
void decide_winner();
string get_msg(Choice winner);
int rand0toN1(int n);

int main(int argc, char *argv[])
{
    srand(time(NULL));    //set randomization
    string input_str;
    int c;
    while (true) {
        cout << "Enter Rock, Paper, Scissors, or Exit: ";
        getline(cin, input_str);
        if (input_str.size() < 1) {
            cout << "Sorry, I don't understand that.\n";
            continue;
        }
        c = input_str[0];
        if (c == 'R' || c == 'r')
            player_choice = rock;
        else if (c == 'P' || c == 'p')
            player_choice = paper;
        else if (c == 'S' || c == 's')
            player_choice = scissors;
        else if (c == 'E' || c == 'e')
            break;
        else {
            cout << "Sorry, I don't understand that.\n";
            continue;
        }
        machine_choice = get_machine_choice();
        int p = (int) player_choice;
        int c = (int) machine_choice;
        cout << "You Choose " << words [p];
        cout << "," << endl;
        cout << "I choose " << words [c];
        cout << "," << endl;
        decide_winner();
    }
    return EXIT_SUCCESS;
}

Choice get_machine_choice() {
    int n = rand0toN1(3);
    if (n == 0) return rock;
    if (n == 1) return paper;
    return scissors;
}

void decide_winner() {
    if (player_choice == machine_choice) {
        cout << "Reult is a tie.\n\n";
        return;
    }
    int p = static_cast<int>(player_choice);
    int c = static_cast<int>(machine_choice);
    if (p - c == 1 || p - c == -2) {
        cout << get_msg(player_choice);
        cout << "Unfortunantly, you win...\n";
    } else {
        cout << get_msg(machine_choice);
        cout << "I WIN, BEEEATCH!!!!\n";
    }
    cout << endl;
}

string get_msg(Choice winner) {
    if (winner == rock)
        return string("Rock smashes scissors, beeatch...");
    else if (winner == paper)
        return string("You know what paper does to rock, COVERAGE!!...");
    else
        return string("CHOP! Scissors cut paper!!....");
}

int rand0toN1(int n) {
    return rand() % n;
}

Answer 4

枚举类是作为c ++ 11标准的一部分引入的。它不会存在于VC2010中。您需要升级到VC2012才能使用此功能。否则从枚举声明中删除“class”。

enum class Choice { rock, paper, scissors }; //Error in vs2010. Drop class.
enum class Choice { rock, paper, scissors }; //Ok in vs2012.
enum Choice { rock, paper, scissors }; //Ok in vs2010.

我似乎无法让Visual C ++ Express（2010）识别枚举类

4 个答案: