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这种枚举是什么意思啊？？？？？？

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这种枚举是什么意思啊？？？？？？

发表于：2008-01-21 20:52:12 楼主

enum week : char{ monday='m', tuesday='t', wednesday='w',thursday='t', friday='f', saturday='s', sunday='s'}things;
things=sunday;

cout < <things;

有错啊

error c2593: 'operator < <' is ambiguous

ivor horton's
beginning visual c++? 2005

enumeration constants are type int by default, but you can also choose to specify the type explicitly by
adding a colon and the type name for the constants following the enumeration type name in the declaration.
you can specify the type for the enumeration constants as any of the signed or unsigned integer
types: short, int, long, and char, or as type bool.
thus, you could define the enumeration representing days of the week as:
enum week: char{ monday, tuesday, wednesday, thursday, friday, saturday, sunday};
here the enumeration constants will be of type char with the first constant as 0. however, with the constants
as type char you might prefer to initialize them explicitly, like this:
enum week : char{ monday='m', tuesday='t', wednesday='w',
thursday='t', friday='f', saturday='s', sunday='s'};
now the values for the constants reflect a little more what they represent, although they do not distinguish
between thursday and tuesday or between saturday and sunday. there is no problem with
having duplicate values for the constants, but of course, all the names must be unique.
here's an example of an enumeration with bool constants:
enum state : bool { on = true, off};
because on has the initial value true, off will be false. if there were subsequent enumerations constants
specified, they would alternate in value by default

发表于：2008-01-21 21:14:201楼得分:0

把things=sunday;
放到函数里阿,不能全局阿

enum xxxx : char

表示枚举的数据类型是char,默认是int

发表于：2008-01-21 21:17:202楼得分:0

这不是iso c++吧～

发表于：2008-01-21 21:23:103楼得分:0

我是放到main函数中的哦

发表于：2008-01-21 21:25:554楼得分:0

c/c++ code


    cout<<（char)things;

发表于：2008-01-21 21:30:225楼得分:0

也可以加上

c/c++ code


ostream& operator<<（ostream& o, week w) {
    return o<<（char)w;
}

发表于：2008-01-22 09:06:456楼得分:0

楼主啊，因为你使用了vc定义枚举的扩展语法，而cout库vc并没有同步扩展，
所以，在你还是编程新手的阶段，不要使用任何只一个编译器支持的特有扩展语法。

发表于：2008-01-22 10:05:057楼得分:0

楼上正解

发表于：2008-01-22 10:20:078楼得分:0

谢谢

发表于：2008-01-22 14:24:539楼得分:0

enum week:char

的目的是要声明一个长度为char的枚举类型。这不是c++的标准语法，而是vc的一个扩展语法。

至于为什么使用operator < <会导致二义性，原因如下：
由于week类型没有指定的operator < <，所以一定要发生类型的隐式转换。

按照c++标准的规定enum类型会被提升为int类型，而按照你的定义enum类型又会被映射为char类型。而operator < <针对int和char都有重载，所以编译器无法判断两个重载函数的优先级，产生了二义性错误

发表于：2008-01-22 14:25:5610楼得分:0

解决方案就是显示指定week被转换到的类型，具体写法看chiyer 的代码

发表于：2008-01-22 14:29:1111楼得分:0

官方支持。。

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您的位置：程序门 -> c/c++ -> c++ 语言

这种 枚举是什么意思啊？？？？？？

这种枚举是什么意思啊？？？？？？