Print text instead of value from C enum

Question

int main        enum Days Sunday Monday Tuesday Wednesday Thursday Friday Saturday      Days TheDay     int j   0     printf  Please enter the day of the week  0 to 6  n       scanf   d   amp j      TheDay   Days j        how to PRINT THE VALUES stored in TheDay    printf   s  TheDay         isnt working    return 0

User · Answer

enums in C don t really work the way you re expecting them to   You can think of them kind of like glorified constants  with a few additional benefits relating to being a collection of such constants   and the text you ve written in for  Sunday  really gets resolved to a number during compilation  the text is ultimately discarded   In short  to do what you really want you ll need to keep an array of the strings or create a function to map from the enum s value to the text you d like to print

User · Answer

i m new to this but a switch statement will defenitely work   include  lt stdio h gt   enum mycolor   int main int argc  const char   argv       enum Days Sunday 1 Monday 2 Tuesday 3 Wednesday 4 Thursday 5 Friday 6 Saturday 7    enum Days TheDay    printf  Please enter the day of the week  0 to 6  n     scanf   d   amp TheDay    switch  TheDay      case Sunday          printf  the selected day is sunday            break      case Monday          printf  the selected day is monday            break      case Tuesday          printf  the selected day is Tuesday            break      case Wednesday          printf  the selected day is Wednesday            break      case Thursday          printf  the selected day is thursday            break      case Friday          printf  the selected day is friday            break      case Saturday          printf  the selected day is Saturaday            break      default          break     return 0

User · Answer

The question is you want write the name just one times  I have an ider like this     define   ENUM situation num        int situation   num         const char       situation   name    situation       const struct             ENUM get other string  -203    using a   ENUM Mirco make it ease to write             ENUM get negative to unsigned  -204             ENUM overflow -205     The following two line showing the expanding for   ENUM         int get no num   -201       const char     get no num name    get no num           int get float to int   -202         const char   get float to int name    float to int name         eRevJson   undef   ENUM     struct sIntCharPtr   int value  const char   p name       This function transform it to string      inline const char   enumRevJsonGetString int num            sIntCharPtr   ptr    sIntCharPtr     amp eRevJson           for  int i   0 i  lt  sizeof eRevJson    sizeof sIntCharPtr  i                  if  ptr i  value    num                    return ptr i  p name                                  return  bad enum value           it uses a struct to insert enum  so that a printer to string could follows each enum value define   int main int argc  char  argv            int enum test   eRevJson get other string      printf  error is  s  number is  d n   enumRevJsonGetString enum test   enum test      gt error is get other string  number is -203    The difference to enum is builder can not report error if the numbers are repeated  if you don t like write number    LINE   could replace it    define     LINE     LINE    define   ENUM situation        int situation        LINE   -   BASELINE -2         const char       situation   name    situation  constexpr int   BASELINE     LINE    constexpr struct         ENUM Sunday         ENUM Monday         ENUM Tuesday         ENUM Wednesday         ENUM Thursday         ENUM Friday         ENUM Saturday    eDays   undef   ENUM inline const char   enumDaysGetString int num        sIntCharPtr   ptr    sIntCharPtr     amp eDays       for  int i   0 i  lt  sizeof eDays    sizeof sIntCharPtr  i              if  ptr i  value    num                return ptr i  p name                      return  bad enum value     int main int argc  char  argv            int d   eDays Wednesday      printf  day  s  number is  d n   enumDaysGetString d   d       d   1      printf  day  s  number is  d n   enumDaysGetString d   d        gt day Wednesday  number is 3                                                                                           gt day Monday  number is 1

User · Answer

Here s a cleaner way to do it with macros    include  lt stdio h gt   include  lt stdlib h gt    define DOW X  S                                                                X Sunday  S X Monday  S X Tuesday  S X Wednesday  S X Thursday  S X Friday  S X Saturday    define COMMA       declare the enum     define DOW ENUM DOW  DOW enum dow       DOW DOW ENUM  COMMA         create an array of strings with the enum names        define DOW ARR DOW    DOW     DOW const char   const dow str           DOW DOW ARR  COMMA            or create a switchy function     static const char   dowstr int i     define DOW CASE D  case D  return  D      switch i            DOW DOW CASE          default  return NULL            int main void        for int i   0  i  lt  7  i            printf    d       s   n   i  dow str i        printf   n        for int i   0  i  lt  7  i            printf    d       s   n   i  dowstr i        return 0      I m not sure that this is totally portable b w preprocessors  but it works with gcc   This is c99 btw  so use c99 strict if you plug it into  the online compiler  ideone

User · Answer

There is another solution  Create your own dynamic enumeration class  Means you have a struct and some function to create a new enumeration  which stores the elements in  a struct and each element has a string for the name  You also need some type to store a individual elements  functions to compare them and so on  Here is an example   include  lt stdarg h gt   include  lt stdbool h gt   include  lt stddef h gt   include  lt stdio h gt   include  lt stdlib h gt   include  lt string h gt    struct Enumeration element T     size t index    struct Enumeration T  parrent    char  name      struct Enumeration T     size t len    struct Enumeration element T elements            void enumeration delete struct Enumeration T  self      if self          while self- gt len--              free self- gt elements self- gt len  name             free self          struct Enumeration T  enumeration create size t len            We do not check for size t overflows  but we should    struct Enumeration T  self malloc sizeof self  sizeof self- gt elements 0   len     if  self          return NULL        self- gt len 0    va list l     va start l len     for size t i 0 i lt len i            const char  name va arg l const char         self- gt elements i  name malloc strlen name  1       if  self- gt elements i  name              enumeration delete self         return NULL            strcpy self- gt elements i  name name       self- gt len          return self      bool enumeration isEqual struct Enumeration element T  a struct Enumeration element T  b      return a- gt parrent  b- gt parrent  amp  amp  a- gt index  b- gt index     bool enumeration isName struct Enumeration element T  a  const char  name      return  strcmp a- gt name name      const char  enumeration getName struct Enumeration element T  a      return a- gt name     struct Enumeration element T  enumeration getFromName struct Enumeration T  self  const char  name      for size t i 0 i lt self- gt len i            if enumeration isName  amp self- gt elements i  name               return  amp self- gt elements i               return NULL       struct Enumeration element T  enumeration get struct Enumeration T  self  size t index      return  amp self- gt elements index      size t enumeration getCount struct Enumeration T  self      return self- gt len     bool enumeration isInRange struct Enumeration T  self  size t index      return index lt self- gt len       int main void      struct Enumeration T  weekdays enumeration create 7  quot Sunday quot   quot Monday quot   quot Tuesday quot   quot Wednesday quot   quot Thursday quot   quot Friday quot   quot Saturday quot      if  weekdays          return 1             printf  quot Please enter the day of the week  0 to 6  n quot      size t j   0    if scanf  quot  zu quot   amp j   1          enumeration delete weekdays       return 1           j j enumeration getCount weekdays     alternative way to make sure j is in range   if  enumeration isInRange weekdays j           enumeration delete weekdays       return 1         struct Enumeration element T  day enumeration get weekdays j         printf  quot  s n quot  enumeration getName day         enumeration delete weekdays      return 0     The functions of enumeration should be in their own translation unit  but i combined them here to make it simpler  The advantage is that this solution is flexible  follows the DRY principle  you can store information along with each element  you can create new enumerations during runtime and you can add new elements during runtime  The disadvantage is that this is complex  needs dynamic memory allocation  can t be used in switch-case  needs more memory and is slower  The question is if you should not use a higher level language in cases where you need this

User · Answer

The way I usually do this is by storing the string representations in a separate array in the same order  then indexing the array with the enum value   const char  DayNames        Sunday    Monday    Tuesday      etc       printf   s   DayNames Sunday       prints  Sunday

User · Answer

I know I am late to the party  but how about this   const char  dayNames        Sunday     Sunday    Monday     Monday     and so on      printf   s   dayNames Sunday       prints  Sunday    This way  you do not have to manually keep the enum and the char  array in sync  If you are like me  chances are that you will later change the enum  and the char  array will print invalid strings  This may not be a feature universally supported  But afaik  most of the mordern day C compilers support this designated initialier style   You can read more about designated initializers here

User · Answer

I use something like this   in a file  EnumToString h     undef DECL ENUM ELEMENT  undef DECL ENUM ELEMENT VAL  undef DECL ENUM ELEMENT STR  undef DECL ENUM ELEMENT VAL STR  undef BEGIN ENUM  undef END ENUM   ifndef GENERATE ENUM STRINGS      define DECL ENUM ELEMENT  element   element       define DECL ENUM ELEMENT VAL  element  value   element   value       define DECL ENUM ELEMENT STR  element  descr   DECL ENUM ELEMENT  element        define DECL ENUM ELEMENT VAL STR  element  value  descr   DECL ENUM ELEMENT VAL  element  value        define BEGIN ENUM  ENUM NAME   typedef enum tag  ENUM NAME      define END ENUM  ENUM NAME   ENUM NAME                const char  GetString  ENUM NAME enum tag  ENUM NAME index    else      define BEGIN ENUM  ENUM NAME  const char   GetString  ENUM NAME  enum tag  ENUM NAME index              switch  index           define DECL ENUM ELEMENT  element   case element  return  element  break       define DECL ENUM ELEMENT VAL  element  value   DECL ENUM ELEMENT  element        define DECL ENUM ELEMENT STR  element  descr   case element  return descr  break       define DECL ENUM ELEMENT VAL STR  element  value  descr   DECL ENUM ELEMENT STR  element  descr         define END ENUM  ENUM NAME   default  return  Unknown value           endif   then in any header file you make the enum declaration  day enum h   include  EnumToString h   BEGIN ENUM Days        DECL ENUM ELEMENT Sunday    will render  Sunday      DECL ENUM ELEMENT Monday    will render  Monday      DECL ENUM ELEMENT STR Tuesday   Tuesday string     will render  Tuesday string      DECL ENUM ELEMENT Wednesday    will render  Wednesday      DECL ENUM ELEMENT VAL STR Thursday  500   Thursday string      will render  Thursday string  and the enum will have 500 as value            and so on      END ENUM MyEnum    then in a file called EnumToString c    include  enum h    define GENERATE ENUM STRINGS     Start string generation   include  enum h                 undef GENERATE ENUM STRINGS      Stop string generation   then in main c   int main int argc  char  argv          Days TheDay   Monday      printf    d -  s n   TheDay  GetStringDay TheDay       will print  1 - Monday       TheDay   Thursday      printf    d -  s n   TheDay  GetStringDay TheDay       will print  500 - Thursday string       return 0      this will generate  automatically  the strings for any enums declared this way and included in  EnumToString c

User · Answer

Enumerations in C are basically syntactical sugar for named lists of automatically-sequenced integer values  That is  when you have this code   int main         enum Days Sunday Monday Tuesday Wednesday Thursday Friday Saturday        Days TheDay   Monday      Your compiler actually spits out this   int main         int TheDay   1     Monday is the second enumeration  hence 1  Sunday would be 0      Therefore  outputting a C enumeration as a string is not an operation that makes sense to the compiler  If you want to have human-readable strings for these  you will need to define functions to convert from enumerations to strings

User · Answer

I like this to have enum in the dayNames  To reduce typing  we can do the following    define EP x   x     x     ENUM PRINT     const char  dayNames       EP Sunday   EP Monday

User · Answer

TheDay maps back to some integer type   So   printf   s   TheDay     Attempts to parse TheDay as a string  and will either print out garbage or crash   printf is not typesafe and trusts you to pass the right value to it   To print out the name of the value  you d need to create some method for mapping the enum value to a string - either a lookup table  giant switch statement  etc

User · Answer

Enumerations in C are numbers that have convenient names inside your code  They are not strings  and the names assigned to them in the source code are not compiled into your program  and so they are not accessible at runtime   The only way to get what you want is to write a function yourself that translates the enumeration value into a string  E g   assuming here that you move the declaration of enum Days outside of main    const char  getDayName enum Days day        switch  day              case Sunday  return  Sunday         case Monday  return  Monday            etc                  Then  later in main     printf   s   getDayName TheDay      Alternatively  you could use an array as a map  e g   const char  dayNames       Sunday    Monday    Tuesday          etc                       printf   s   dayNames TheDay      But here you would probably want to assign Sunday   0 in the enumeration to be safe    I m not sure if the C standard requires compilers to begin enumerations from 0  although most do  I m sure someone will comment to confirm or deny this

[c] Print text instead of value from C enum

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