enum与typedef-enum的用法

在程序中，可能需要为某些整数定义一个别名，我们可以利用预处理指令#define来完成这项工作，您的代码可能是：#defineMON1#defineTUE2#defineWED3#defineTHU4#defineFRI5#defineSAT6#defineSUN7在此，我们定义一种新的数据类型，希望它能完成同样的工作。这种新的数据类型叫枚举型。1.定义一种新的数据类型-枚举型以下代码定义了这种新的数据类型-枚举型enumDAY{MON=1,TUE,WED,THU,FRI,SAT,SUN};(1)枚举型是一个集合，集合中的元素(枚举成员)是一些命名的整型常量，元素之间用逗号,隔开。(2)DAY是一个标识符，可以看成这个集合的名字，是一个可选项，即是可有可无的项。(3)第一个枚举成员的默认值为整型的0，后续枚举成员的值在前一个成员上加1。(4)可以人为设定枚举成员的值，从而自定义某个范围内的整数。(5)枚举型是预处理指令#define的替代。(6)类型定义以分号;结束。2.使用枚举类型对变量进行声明新的数据类型定义完成后，它就可以使用了。我们已经见过最基本的数据类型，如：整型int,单精度浮点型float,双精度浮点型double,字符型char,短整型short等等。用这些基本数据类型声明变量通常是这样：chara;//变量a的类型均为字符型charcharletter;intx,y,z;//变量x,y和z的类型均为整型intintnumber;doublem,n;doubleresult;//变量result的类型为双精度浮点型double既然枚举也是一种数据类型，那么它和基本数据类型一样也可以对变量进行声明。方法一：枚举类型的定义和变量的声明分开enumDAY{MON=1,TUE,WED,THU,FRI,SAT,SUN};enumDAYyesterday;enumDAYtoday;enumDAYtomorrow;//变量tomorrow的类型为枚举型enumDAYenumDAYgood_day,bad_day;//变量good_day和bad_day的类型均为枚举型enumDAY方法二：类型定义与变量声明同时进行：enum//跟第一个定义不同的是，此处的标号DAY省略，这是允许的。{saturday,sunday=0,monday,tuesday,wednesday,thursday,friday}workday;//变量workday的类型为枚举型enumDAYenumweek{Mon=1,Tue,Wed,Thu,FriSat,Sun}days;//变量days的类型为枚举型enumweekenumBOOLEAN{false,true}end_flag,match_flag;//定义枚举类型并声明了两个枚举型变量方法三：用typedef关键字将枚举类型定义成别名，并利用该别名进行变量声明：typedefenumworkday{saturday,sunday=0,monday,tuesday,wednesday,thursday,friday}workday;//此处的workday为枚举型enumworkday的别名workdaytoday,tomorrow;//变量today和tomorrow的类型为枚举型workday，即enumworkday也可以：typedefenum{saturday,sunday=0,monday,tuesday,wednesday,thursday,friday}workday;//此处的workday为枚举型enumworkday的别名workdaytoday,tomorrow;//变量today和tomorrow的类型为枚举型workday，即enumworkday也可以用这种方式：typedefenumworkday{saturday,sunday=0,monday,tuesday,wednesday,thursday,friday};workdaytoday,tomorrow;//变量today和tomorrow的类型为枚举型workday，即enumworkday注意：同一个程序中不能定义同名的枚举类型，不同的枚举类型中也不能存在同名的命名常量。错误示例如下所示：错误声明一：存在同名的枚举类型typedefenum{wednesday,thursday,friday}workday;typedefenumWEEK{saturday,sunday=0,monday,}workday;错误声明二：存在同名的枚举成员typedefenum{wednesday,thursday,friday}workday_1;typedefenumWEEK{wednesday,sunday=0,monday,}workday_2;3.使用枚举类型的变量3.1对枚举型的变量赋值。实例将枚举类型的赋值与基本数据类型的赋值进行了对比：方法一：先声明变量，再对变量赋值#include/SPANstdio.henumDAY{MON=1,TUE,WED,THU,FRI,SAT,SUN};voidmain(){intx,y,z;x=10;y=20;z=30;enumDAYyesterday,today,tomorrow;yesterday=MON;today=TUE;tomorrow=WED;printf(%d%d%d\n,yesterday,today,tomorrow);}方法二：声明变量的同时赋初值#include/SPANstdio.henumDAY{MON=1,TUE,WED,THU,FRI,SAT,SUN};voidmain(){intx=10,y=20,z=30;enumDAYyesterday=MON,today=TUE,tomorrow=WED;printf(%d%d%d\n,yesterday,today,tomorrow);}方法三：定义类型的同时声明变量，然后对变量赋值。#include/SPANstdio.henumDAY{MON=1,TUE,WED,THU,FRI,SAT,SUN}yesterday,today,tomorrow;intx,y,z;voidmain(){x=10;y=20;z=30;yesterday=MON;today=TUE;tomorrow=WED;printf(%d%d%d\n,x,y,z);//输出：102030printf(%d%d%d\n,yesterday,today,tomorrow);//输出：123}方法四：类型定义，变量声明，赋初值同时进行。#include/SPANstdio.henumDAY{MON=1,TUE,WED,THU,FRI,SAT,SUN}yesterday=MON,today=TUE,tomorrow=WED;intx=10,y=20,z=30;voidmain(){printf(%d%d%d\n,x,y,z);//输出：102030printf(%d%d%d\n,yesterday,today,tomorrow);//输出：123}3.2对枚举型的变量赋整数值时，需要进行类型转换。#include/SPANstdio.henumDAY{MON=1,TUE,WED,THU,FRI,SAT,SUN};voidmain(){enumDAYyesterday,today,tomorrow;yesterday=TUE;today=(enumDAY)(yesterday+1);//类型转换tomorrow=(enumDAY)30;//类型转换//tomorrow=3;//错误printf(%d%d%d\n,yesterday,today,tomorrow);//输出：2330}3.3使用枚举型变量#include/SPANstdio.henum{BELL='\a',BACKSPACE='\b',HTAB='\t',RETURN='\r',NEWLINE='\n',VTAB='\v',SPACE=''};enumBOOLEAN{FALSE=0,TRUE}match_flag;voidmain(){intindex=0;intcount_of_letter=0;intcount_of_space=0;charstr[]=I'mElyefod;match_flag=FALSE;for(;str[index]!='\0';index++)if(SPACE!=str[index])count_of_letter++;else{match_flag=(enumBOOLEAN)1;count_of_space++;}printf(%s%dtimes%c,match_flag?match:notmatch,count_of_space,NEWLINE);printf(countofletters:%d%c%c,count_of_letter,NEWLINE,RETURN);}输出：match2timescountofletters:10Pressanykeytocontinue4.枚举类型与sizeof运算符#include/SPANstdio.henumescapes{BELL='\a',BACKSPACE='\b',HTAB='\t',RETURN='\r',NEWLINE='\n',VTAB='\v',SPACE=''};enumBOOLEAN{FALSE=0,TRUE}match_flag;voidmain(){printf(%dbytes\n,sizeof(enumescapes));//4bytesprintf(%dbytes\n,sizeof(escapes));//4bytesprintf(%dbytes\n,sizeof(enumBOOLEAN));//4bytesprintf(%dbytes\n,sizeof(BOOLEAN));//4bytesprintf(%dbytes\n,sizeof(match_flag));//4bytesprintf(%dbytes\n,sizeof(SPACE));//4bytesprintf(%dbytes\n,sizeof(NEWLINE));//4bytesprintf(%dbytes\n,sizeof(FALSE));//4bytesprintf(%dbytes\n,sizeof(0));//4bytes}5.综合举例#include/SPANstdio.henumSeason//注意这里如果放在下面，后面就不能直接那样声明{spring,summer=100,fall=96,winter};typedefenum{Monday,Tuesday,Wednesday,Thursday,Friday,Saturday,Sunday}Weekday;voidmain(){printf(%d\n,spring);//0printf(%d,%c\n,summer,summer);//100,dprintf(%d\n,fall+winter);//193SeasonmySeason=winter;//就是这里，看上面的定义，也可以enumSeasonmySeasonif(winter==mySeason)printf(mySeasoniswinter\n);//mySeasoniswinterintx=100;if(x==summer)printf(xisequaltosummer\n);//xisequaltosummerprintf(%dbytes\n,sizeof(spring));//4bytesprintf(sizeofWeekdayis:%d\n,sizeof(Weekday));//sizeofWeekdayis:4Weekdaytoday=Saturday;Weekdaytomorrow;if(today==Mon