Creating a string list and an enum list from a C++ macro

Question

In order to make my code shorter and easier to change I want to replace something like

enum{ E_AAA, E_BBB, E_CCC };
static const char *strings{\"AAA\", \"BBB         


        

Answer 1

Here is my solution:

#define FRUITS(fruit) \
  fruit(Apple)        \
  fruit(Orange)       \
  fruit(Banana)       

#define CREATE_ENUM(name) \
  F_##name,

#define CREATE_STRINGS(name) \
  #name,

The trick is that 'fruit' is an argument of the macro 'FRUITS' and will be replaced by what ever you pass to. For example:

FRUITS(CREATE_ENUM)

will expand to this:

F_Apple, F_Orange, F_Banana, 

Lets create the enum and the string array:

enum fruit {
  FRUITS(CREATE_ENUM)
};

const char* fruit_names[] = {
  FRUITS(CREATE_STRINGS)
};

Answer 2

Here a solution I learned a few days ago. The simplified version that attends your question is:

#define ENUM_MACRO(name, v1, v2, v3, v4, v5, v6, v7)\
    enum name { v1, v2, v3, v4, v5, v6, v7};\
    const char *name##Strings[] = { #v1, #v2, #v3, #v4, #v5, #v6, #v7};

ENUM_MACRO(Week, Sun, Mon, Tue, Wed, Thu, Fri, Sat);

But you can have an improved version, with a function call, like this:

#define ENUM_MACRO(name, v1, v2, v3, v4, v5, v6, v7)\
    enum name { v1, v2, v3, v4, v5, v6, v7};\
    const char *name##Strings[] = { #v1, #v2, #v3, #v4, #v5, #v6, #v7};\
    const char *name##ToString(value) { return name##Strings[value]; }

ENUM_MACRO(Week, Sun, Mon, Tue, Wed, Thu, Fri, Sat);

This will grow to be:

  enum Week { Sun, Mon, Tue, Wed, Thu, Fri, Sat}; 
  const char *WeekStrings[] = { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"}; 
  const char *WeekToString(value) { return WeekStrings[value]; };

You can even use an offset for the first element, like this one:

#define ENUM_MACRO(name, offset, v1, v2, v3, v4, v5, v6, v7)\
    enum name { v1 =  offset, v2, v3, v4, v5, v6, v7};\
    const char *name##Strings[] = { #v1, #v2, #v3, #v4, #v5, #v6, #v7};\
    const char *name##ToString(value) { return name##Strings[value - offset ]; }

ENUM_MACRO(Week, 1, Sun, Mon, Tue, Wed, Thu, Fri, Sat);

I hope this helps.

Take care, Beco

Reference:

Print the month question, by Kush, answer by Danny Varod