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cppcooper/has_a.cpp

Created March 15, 2022 06:23
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member detection with templates/macro
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has_a.cpp
#include <type_traits>
#define DECLARE_HASA(what) \
template<typename T, typename = int> struct has_##what : std::false_type { };\
template<typename T> struct has_##what<T, decltype((void) T::what, 0)> : std::true_type {};
DECLARE_HASA(when) //declares above statement with 'when' replacing 'what'
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