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Converting Enum Type Variables to Strings
In C and C , enum types provide a convenient way to represent a finite set of values. However, when working with printf or other formatting functions, it can be challenging to convert enums to their corresponding string representations.
Naive Solution
A simple solution involves creating a switch-case statement for each enum type, mapping each value to its corresponding string:
enum OS_type { Linux, Apple, Windows }; const char* ToString(OS_type v) { switch (v) { case Linux: return "Linux"; case Apple: return "Apple"; case Windows: return "Windows"; default: return "[Unknown OS_type]"; } }
However, this approach becomes cumbersome and error-prone as the number of enum values increases.
Using Boost.Preprocessor
The Boost.Preprocessor library offers a more elegant solution. It allows you to generate such conversion functions dynamically based on your enum definitions:
#include <boost/preprocessor.hpp> #define X_DEFINE_ENUM_WITH_STRING_CONVERSIONS_TOSTRING_CASE(r, data, elem) \ case elem : return BOOST_PP_STRINGIZE(elem); #define DEFINE_ENUM_WITH_STRING_CONVERSIONS(name, enumerators) \ enum name { \ BOOST_PP_SEQ_ENUM(enumerators) \ }; \ \ inline const char* ToString(name v) \ { \ switch (v) \ { \ BOOST_PP_SEQ_FOR_EACH( \ X_DEFINE_ENUM_WITH_STRING_CONVERSIONS_TOSTRING_CASE, \ name, \ enumerators \ ) \ default: return "[Unknown " BOOST_PP_STRINGIZE(name) "]"; \ } \ }
The first macro (beginning with X_) generates the enumeration, and the second (DEFINE_ENUM_WITH_STRING_CONVERSIONS) generates the ToString function.
Example Usage
For the OS_type enumeration, the definition using the macro would be:
DEFINE_ENUM_WITH_STRING_CONVERSIONS(OS_type, (Linux)(Apple)(Windows))
You can then utilize the ToString function to convert enum values to strings:
#include <iostream> int main() { OS_type t = Windows; std::cout << ToString(t) << " " << ToString(Apple) << std::endl; return 0; }
This solution provides a generic approach to converting enums to strings, reducing the need for repetitive switch-case statements and improving code maintenance.
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