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Subject: [boost] Adding helpful requires macros to the enable_if utility
From: paul Fultz (pfultz2_at_[hidden])
Date: 2014-06-27 12:10:33

These following set of macros, I have found very useful in C++: #define BOOST_ERROR_PARENTHESIS_MUST_BE_PLACED_AROUND_THE_RETURN_TYPE(...) __VA_ARGS__>::type #define BOOST_FUNCTION_REQUIRES(...) typename boost::enable_if_c<(__VA_ARGS__), BOOST_ERROR_PARENTHESIS_MUST_BE_PLACED_AROUND_THE_RETURN_TYPE #define BOOST_CLASS_REQUIRES(...) typename boost::enable_if_c<(__VA_ARGS__)>::type #define BOOST_REQUIRES(...) typename boost::enable_if_c<(__VA_ARGS__), int>::type = 0 Which I use like the following For functions:     template <class T>     BOOST_FUNCTION_REQUIRES(boost::is_arithmetic<T>::value)     (T) foo(T t) { return t; } And C++11 functions:     template <class T, BOOST_REQUIRES(boost::is_arithmetic<T>())>     T foo(T t) { return t; } Class specializations:     template <class T, class Enable = void>     class A { ... };     template <class T>     class A<T, BOOST_CLASS_REQUIRES(is_integral<T>())> { ... };     template <class T>     class A<T, BOOST_CLASS_REQUIRES(is_float<T>())> { ... }; It would be nice if these were the added with the enable_if utility with boost. Thanks, Paul

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