在c++中，字符串不是一等公民。字符串操作是通过标准库完成的。我想，这就是原因。另外，c++使用分支表优化来优化开关case语句。看看这个链接。

http://en.wikipedia.org/wiki/Switch_statement

    cout << "\nEnter word to select your choice\n"; 
    cout << "ex to exit program (0)\n";     
    cout << "m     to set month(1)\n";
    cout << "y     to set year(2)\n";
    cout << "rm     to return the month(4)\n";
    cout << "ry     to return year(5)\n";
    cout << "pc     to print the calendar for a month(6)\n";
    cout << "fdc      to print the first day of the month(1)\n";
    cin >> c;
    cout << endl;
    a = c.compare("ex") ?c.compare("m") ?c.compare("y") ? c.compare("rm")?c.compare("ry") ? c.compare("pc") ? c.compare("fdc") ? 7 : 6 :  5  : 4 : 3 : 2 : 1 : 0;
    switch (a)
    {
        case 0:
            return 1;

        case 1:                   ///m
        {
            cout << "enter month\n";
            cin >> c;
            cout << endl;
            myCalendar.setMonth(c);
            break;
        }
        case 2:
            cout << "Enter year(yyyy)\n";
            cin >> y;
            cout << endl;
            myCalendar.setYear(y);
            break;
        case 3:
             myCalendar.getMonth();
            break;
        case 4:
            myCalendar.getYear();
        case 5:
            cout << "Enter month and year\n";
            cin >> c >> y;
            cout << endl;
            myCalendar.almanaq(c,y);
            break;
        case 6:
            break;

    }

Why not? You can use switch implementation with equivalent syntax and same semantics. The C language does not have objects and strings objects at all, but strings in C is null terminated strings referenced by pointer. The C++ language have possibility to make overload functions for objects comparision or checking objects equalities. As C as C++ is enough flexible to have such switch for strings for C language and for objects of any type that support comparaison or check equality for C++ language. And modern C++11 allow to have this switch implementation enough effective.

你的代码是这样的:

std::string name = "Alice";

std::string gender = "boy";
std::string role;

SWITCH(name)
  CASE("Alice")   FALL
  CASE("Carol")   gender = "girl"; FALL
  CASE("Bob")     FALL
  CASE("Dave")    role   = "participant"; BREAK
  CASE("Mallory") FALL
  CASE("Trudy")   role   = "attacker";    BREAK
  CASE("Peggy")   gender = "girl"; FALL
  CASE("Victor")  role   = "verifier";    BREAK
  DEFAULT         role   = "other";
END

// the role will be: "participant"
// the gender will be: "girl"

可以使用更复杂的类型，例如std::pairs或任何支持相等操作(或快速模式的比较)的结构或类。

特性

支持比较或检验相等性的任何类型的数据 构建级联嵌套开关语句的可能性。 打破case语句的可能性 使用非常量大小写表达式的可能性 可以通过树搜索启用快速静态/动态模式(适用于c++ 11)

汉译语的差异在于语言的转换

大写的字 CASE语句需要括号 语句末尾不允许使用分号 冒号':' at CASE语句不被允许 在CASE语句的末尾需要一个BREAK或FALL关键字

对于c++ 97语言采用线性搜索。 对于c++ 11和更现代的可能使用快速模式wuth树搜索，其中CASE中的return语句变得不允许。 C语言实现中使用char*类型和以零结尾的字符串比较。

阅读更多关于这个开关实现的信息。

在c++中，字符串不是一等公民。字符串操作是通过标准库完成的。我想，这就是原因。另外，c++使用分支表优化来优化开关case语句。看看这个链接。

http://en.wikipedia.org/wiki/Switch_statement

这是因为c++将开关转换为跳转表。它对输入数据执行简单的操作，并在不进行比较的情况下跳转到适当的地址。因为字符串不是一个数字，而是一个数字数组，所以c++不能从它创建一个跳转表。

movf    INDEX,W     ; move the index value into the W (working) register from memory
addwf   PCL,F       ; add it to the program counter. each PIC instruction is one byte
                    ; so there is no need to perform any multiplication. 
                    ; Most architectures will transform the index in some way before 
                    ; adding it to the program counter

table                   ; the branch table begins here with this label
    goto    index_zero  ; each of these goto instructions is an unconditional branch
    goto    index_one   ; of code
    goto    index_two
    goto    index_three

index_zero
    ; code is added here to perform whatever action is required when INDEX = zero
    return

index_one
...

(代码来自维基百科https://en.wikipedia.org/wiki/Branch_table)

在c++中，你只能在int和char上使用switch语句