前言

enum Day
{mon, tue, wed, thu, fir, sat, sun};
枚举类型是为了减少繁多的整数定义。诸如mon（默认=0）,tue这些是枚举符（int类型的常量）对应一个数字。

  • 可以给枚举列表中的常量赋值
  • 没有赋值的枚举符会根据前面被赋予的常量++

概念

mon, tue，把这些看作常量。

定义

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enum Day    //Day是类型名，可不写
{
   mon, tue, wed = 1, thu, fir, sat, sun
}day;       //变量名

用法

  • 给枚举变量赋值，然后输出
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enum Day
{
    mon, tue, wed, thu, fir, sat, sun
};

int main()
{
    enum Day day;//定义变量
    day = tue;
    printf("%d", day);
    return 0;
}
  • 可以用for循环遍历元素(要依赖连续的++值，中间不能有赋值)
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for(day = wed; day <= sun; day++)
    printf("%d ",day);          //输出1， 2， 3， 4，5

示例

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/* enum.c -- uses enumerated values */
#include <stdio.h>
#include <string.h>    // for strcmp(), strchr()
#include <stdbool.h>   // C99 feature
char * s_gets(char * st, int n);
//枚举类型（常量的数组）
enum spectrum {red, orange, yellow, green, blue, violet};
//字符串数组
const char * colors[] = {"red", "orange", "yellow",
    "green", "blue", "violet"};
#define LEN 30

int main(void)
{
    char choice[LEN];
    enum spectrum color;//定义color变量表示枚举符（常量）
    bool color_is_found = false;
    
    puts("Enter a color (empty line to quit):");
    while (s_gets(choice, LEN) != NULL && choice[0] != '\0')
    {
        for (color = red; color <= violet; color++)//常量的使用
        {
            if (strcmp(choice, colors[color]) == 0)
            {
                color_is_found = true;
                break;
            }
        }
        if (color_is_found)
            switch(color)
        {
            case red    : puts("Roses are red.");
                break;
            case orange : puts("Poppies are orange.");
                break;
            case yellow : puts("Sunflowers are yellow.");
                break;
            case green  : puts("Grass is green.");
                break;
            case blue   : puts("Bluebells are blue.");
                break;
            case violet : puts("Violets are violet.");
                break;
        }
        else
            printf("I don't know about the color %s.\n", choice);
        color_is_found = false;
        puts("Next color, please (empty line to quit):");
    }
    puts("Goodbye!");
    
    return 0;
}

char * s_gets(char * st, int n)
{
    char * ret_val;
    char * find;
    
    ret_val = fgets(st, n, stdin);
    if (ret_val)
    {
        find = strchr(st, '\n');   // look for newline
        if (find)                  // if the address is not NULL,
            *find = '\0';          // place a null character there
        else
            while (getchar() != '\n')
                continue;          // dispose of rest of line
    }
    return ret_val;
}