enum to string in modern C++11 / C++14 / C++17 and future C++20

Question

Contrary to all other similar questions, this question is about using the new C++ features.

• 2008 c Is there a simple way to convert C++ enum to string?
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Answer 1

The following solution is based on a std::array for a given enum.

For enum to std::string conversion we can just cast the enum to size_t and lookup the string from the array. The operation is O(1) and requires no heap allocation.

#include 
#include 
#include 

#include 
#include 
#include 

#define STRINGIZE(s, data, elem) BOOST_PP_STRINGIZE(elem)

// ENUM
// ============================================================================
#define ENUM(X, SEQ) \
struct X {   \
    enum Enum {BOOST_PP_SEQ_ENUM(SEQ)}; \
    static const std::array array_of_strings() { \
        return {{BOOST_PP_SEQ_ENUM(BOOST_PP_SEQ_TRANSFORM(STRINGIZE, 0, SEQ))}}; \
    } \
    static std::string to_string(Enum e) { \
        auto a = array_of_strings(); \
        return a[static_cast(e)]; \
    } \
}

For std::string to enum conversion we would have to make a linear search over the array and cast the array index to enum.

Try it here with usage examples: http://coliru.stacked-crooked.com/a/e4212f93bee65076

Edit: Reworked my solution so the custom Enum can be used inside a class.