C语言 枚举类型

#include <stdio.h>

enum&nbsp;week&nbsp;{&nbsp;End,&nbsp;Monday,&nbsp;Tuesday,&nbsp;Wednesday,&nbsp;Thursday,&nbsp;Friday,&nbsp;Saturday,&nbsp;Sunday&nbsp;};

void&nbsp;monday(void){
  puts(&quot;星期一&quot;);
}

void&nbsp;tuesday(void){
  puts(&quot;星期二&quot;);
}

void&nbsp;wednesday(void){
  puts(&quot;星期三&quot;);
}

void&nbsp;thursday(void){
  puts(&quot;星期四&quot;);
}

void&nbsp;friday(void){
  puts(&quot;星期五&quot;);
}

void&nbsp;saturday(void){
  puts(&quot;星期六&quot;);
}

void&nbsp;sunday(void){
  puts(&quot;星期天&quot;);
}

enum&nbsp;week&nbsp;select(void){
  int&nbsp;tmp;
  
  do&nbsp;{
    printf(&quot;0.&nbsp;结束,&nbsp;1.&nbsp;星期一,&nbsp;2.&nbsp;星期二,&nbsp;3.&nbsp;星期三,&nbsp;4.&nbsp;星期四,&nbsp;5.&nbsp;星期五,&nbsp;6.&nbsp;星期六,&nbsp;7.&nbsp;星期天\n&quot;);
    puts(&quot;请选择：&quot;);&nbsp;
    scanf(&quot;%d&quot;,&nbsp;&amp;tmp);
  }while&nbsp;(tmp&nbsp;&lt;&nbsp;End&nbsp;||&nbsp;tmp&nbsp;&gt;&nbsp;Sunday);
  return&nbsp;tmp;
}

int&nbsp;main(void){
  enum&nbsp;week&nbsp;selected;&nbsp;&nbsp;// 声明 enum week 型 的变量 selected
  
  do{
    switch&nbsp;(selected&nbsp;=&nbsp;select()){
      case&nbsp;Monday&nbsp;:
        monday();
      &nbsp;&nbsp;  break;
      case&nbsp;Tuesday&nbsp;:
        tuesday();&nbsp;
      &nbsp;  break;
      case&nbsp;Wednesday&nbsp;:
      &nbsp;&nbsp;&nbsp;&nbsp;wednesday();&nbsp;
        break;
      case&nbsp;Thursday&nbsp;:
      &nbsp;&nbsp;&nbsp;&nbsp;thursday();&nbsp;
        break;
      case&nbsp;Friday&nbsp;:
      &nbsp;&nbsp;&nbsp;&nbsp;friday();&nbsp;
        break;
      case&nbsp;Saturday&nbsp;:
      &nbsp;&nbsp;&nbsp;&nbsp;saturday();&nbsp;
        break;
      case&nbsp;Sunday&nbsp;:
      &nbsp;&nbsp;&nbsp;&nbsp;sunday();&nbsp;
        break;
    }
  }while&nbsp;(selected&nbsp;!=&nbsp;End);
  
  return&nbsp;0;
}

运行结果：

enum week { End, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday };

是枚举类型的声明，它表示了所有可用值的集合。其中，week 被称为枚举名。写在｛｝中的 End, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday 是枚举常量。

注：枚举名不是类型名。类型名称不是 week 型，而是 enum week 型。

如果在没有赋值给枚举常量赋值的情况下，枚举常量默认对应的值是从0开始按顺序为枚举常量定义了相应的整数值。实际上，这些值也能根据需要任意设置，只要在枚举常量的名称后面写上赋值运算符 “=” 和值就行了。

enum week { Monday = 1, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday, End };

通过赋值运算符 “ = ” 赋值的枚举常量，其值为给定值，没有给定值的枚举常量，其值为前一个枚举常量加1。

#include <stdio.h>

enum&nbsp;week&nbsp;{&nbsp;Monday&nbsp;=&nbsp;1,&nbsp;Tuesday,&nbsp;Wednesday,&nbsp;Thursday,&nbsp;Friday,&nbsp;Saturday,&nbsp;Sunday,&nbsp;End&nbsp;};

void&nbsp;monday(void){
  puts(&quot;星期一&quot;);
}

void&nbsp;tuesday(void){
  puts(&quot;星期二&quot;);
}

void&nbsp;wednesday(void){
  puts(&quot;星期三&quot;);
}

void&nbsp;thursday(void){
  puts(&quot;星期四&quot;);
}

void&nbsp;friday(void){
  puts(&quot;星期五&quot;);
}

void&nbsp;saturday(void){
  puts(&quot;星期六&quot;);
}

void&nbsp;sunday(void){
  puts(&quot;星期天&quot;);
}

enum&nbsp;week&nbsp;select(void){
  int&nbsp;tmp;
  
  do&nbsp;{
    printf(&quot;1.&nbsp;星期一,&nbsp;2.&nbsp;星期二,&nbsp;3.&nbsp;星期三,&nbsp;4.&nbsp;星期四,&nbsp;5.&nbsp;星期五,&nbsp;6.&nbsp;星期六,&nbsp;7.&nbsp;星期天,&nbsp;8.&nbsp;结束\n&quot;);
    puts(&quot;请选择：&quot;);&nbsp;
    scanf(&quot;%d&quot;,&nbsp;&amp;tmp);
  }while&nbsp;(tmp&nbsp;&lt;&nbsp;Monday&nbsp;||&nbsp;tmp&nbsp;&gt;&nbsp;End);&nbsp;&nbsp;// 将 End 在枚举类型末端，星期一 位于首端 
  return&nbsp;tmp;
}

int&nbsp;main(void){
  enum&nbsp;week&nbsp;selected;&nbsp;&nbsp;&nbsp;// 声明 enum week 型 的变量 selected
  
  do{
    switch&nbsp;(selected&nbsp;=&nbsp;select()){
      case&nbsp;Monday&nbsp;:
        monday();
      &nbsp;&nbsp;  break;
      case&nbsp;Tuesday&nbsp;:
        tuesday();&nbsp;
      &nbsp;  break;
      case&nbsp;Wednesday&nbsp;:
      &nbsp;&nbsp;&nbsp;&nbsp;wednesday();&nbsp;
        break;
      case&nbsp;Thursday&nbsp;:
      &nbsp;&nbsp;&nbsp;&nbsp;thursday();&nbsp;
        break;
      case&nbsp;Friday&nbsp;:
      &nbsp;&nbsp;&nbsp;&nbsp;friday();&nbsp;
        break;
      case&nbsp;Saturday&nbsp;:
      &nbsp;&nbsp;&nbsp;&nbsp;saturday();&nbsp;
        break;
      case&nbsp;Sunday&nbsp;:
      &nbsp;&nbsp;&nbsp;&nbsp;sunday();&nbsp;
        break;
    }
  }while&nbsp;(selected&nbsp;!=&nbsp;End);
  
  return&nbsp;0;
}

运行结果：

enum { MATGEMATICS, ADVANCED_MATHEMATICS = 0 };

程序中的枚举名可以省略，多个枚举常量也允许具有相同的值。

#include <stdio.h>

enum&nbsp;{&nbsp;MATGEMATICS,&nbsp;ADVANCED_MATHEMATICS&nbsp;=&nbsp;0&nbsp;};

void&nbsp;mathematics(void){
  puts(&quot;数学&quot;);
}

void&nbsp;advanced_mathematics(void){
  puts(&quot;高等数学&quot;);
}


int&nbsp;main(void){
  int&nbsp;tmp;
  
  puts(&quot;请选择：&quot;);
  scanf(&quot;%d&quot;,&nbsp;&amp;tmp);
  
  switch&nbsp;(tmp){
      case&nbsp;MATGEMATICS&nbsp;:
        mathematics();
      &nbsp;&nbsp;  break;
  }
  
  switch&nbsp;(tmp){
      case&nbsp;ADVANCED_MATHEMATICS&nbsp;:
        advanced_mathematics();
      &nbsp;&nbsp;  break;
  }
  
  return&nbsp;0;
}

运行结果：