make_enum

Macros for C/C++ that are used to define enumerations and their helper functions. The enum macros should work with any standards compliant C/C++ compiler. The enum class macros require a C++11 compiler. The macros have been tested with GCC, Clang, and MSVC++.

Setup

Just add make_enum.h to your project. There is no compilation step. The macros in make_enum.h cause the C/C++ preprocess to automatically generate the code and pass it directly to the compiler as part of the compilation unit.

Usage

The macros in make_enum.h are divided into "declaration" macros (that belong in header files) and "definition" macros (that belong in source files). It is done this way because it is difficult to portably and safely inline the helper functions in a header. The following is typically all you need to do to use these macros to declare and define an enumeration along with all of its helper functions:

Header File

As show below, set up a FOREACH macro that can apply an X macro for each element in the enumeration. In order to generate element names like "MyEnum::FOO", an additional EnumName parameter needs to be passed through the FOREACH macro to the X macro. Then, add the either the MAKE_ENUM_DECLARATION() or MAKE_ENUM_CLASS_DECLARATION to your header to declare the enumeration and its helper functions:

#include "make_enum.h"
#define FOREACH_IN_MY_ENUM(EnumName, X) \
    X(EnumName, FOO, 0)                 \
    X(EnumName, BAR, 1)                 \
    X(EnumName, BAZ, 2)
MAKE_ENUM_DECLARATION(MyEnum, FOREACH_IN_MY_ENUM)

Replace MyEnum and FOREACH_IN_MY_ENUM above with the name and elements of the enumeration.

For scoped enumerations in modern C++, use MAKE_ENUM_CLASS_DECLARATION() instead of MAKE_ENUM_DECLARATION().

See X Macros on Wikipedia for more information on how X Macros work.

Source File

Add the corresponding MAKE_ENUM_DEFINITION() or MAKE_ENUM_CLASS_DEFINITION() to your source file to define the helper functions:

#include "my_header.h"
MAKE_ENUM_DEFINITION(MyEnum, FOREACH_IN_MY_ENUM)

Replace FOREACH_IN_MY_ENUM with the name of the FOREACH macro that was passed into the corresponding MAKE_ENUM_DEFINITION() call in the header file.

For scoped enumerations in modern C++, use MAKE_ENUM_CLASS_DEFINITION() instead of MAKE_ENUM_DEFINITION().

Helper Functions

C Helper Functions

The following C helper functions are generated for each enumeration where <EnumName> should be replaced with the name of the enumeration:

• const char*
  <EnumName>_ToString(enum EnumName e,
                      int with_enum_name,
                      int with_element_name);

• int
  <EnumName>_FromString(enum EnumName* e,
                        const char* s);

• int
  <EnumName>_IsValid(enum EnumName e);

C++ Helper Functions

The C++ helper functions include all of the C helper functions plus the following overloaded functions that do not include the name of the enumeration in the name of the function:

• std::string
  ToString(EnumName e,
           bool with_enum_name,
           bool with_element_name);

  If e is an enum, ToString(e) defaults to return just the element name, e.g., FOO. If e is an ename class, ToString(e) defaults to return the scoped name, e.g., MyEnum::FOO.

• bool
  FromString(EnumName& e,
             const std::string& s)

• std::ostream&
  operator<<(std::ostream& ostrm,
             EnumName e);

• std::istream&
  operator>>(std::istream& istrm,
             EnumName& e);

• bool
  IsValid(EnumName e);