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Template simplifications

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Switch count_t to use constexpr_sum (under non-MSVC), and then make
all_of_t/any_of_t use it instead of doing the sum itself.

For MSVC, count_t is still done using template recursion, but
all_of_t/any_of_t can also make use of it.
This commit is contained in:
Jason Rhinelander 2016-09-08 17:45:53 -04:00
parent 260b26b3d6
commit 5aa2cd5eb9
1 changed files with 12 additions and 17 deletions
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29
include/pybind11/common.h
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@ -342,22 +342,24 @@ constexpr size_t constexpr_sum() { return 0; }
template <typename T, typename... Ts> template <typename T, typename... Ts>
constexpr size_t constexpr_sum(T n, Ts... ns) { return size_t{n} + constexpr_sum(ns...); } constexpr size_t constexpr_sum(T n, Ts... ns) { return size_t{n} + constexpr_sum(ns...); }
/// Return true if all/any Ts satify Predicate<T> // Counts the number of types in the template parameter pack matching the predicate
#if !defined(_MSC_VER) #if !defined(_MSC_VER)
template <template<typename> class Predicate, typename... Ts> template <template<typename> class Predicate, typename... Ts>
using all_of_t = bool_constant<(constexpr_sum(Predicate<Ts>::value...) == sizeof...(Ts))>; using count_t = std::integral_constant<size_t, constexpr_sum(Predicate<Ts>::value...)>;
template <template<typename> class Predicate, typename... Ts>
using any_of_t = bool_constant<(constexpr_sum(Predicate<Ts>::value...) > 0)>;
#else #else
// MSVC workaround (2015 Update 3 has issues with some member type aliases and constexpr) // MSVC workaround (2015 Update 3 has issues with some member type aliases and constexpr)
template <template<typename> class P, typename...> struct all_of_t : std::true_type { }; template <template<typename> class Predicate, typename... Ts> struct count_t;
template <template<typename> class P, typename T, typename... Ts> template <template<typename> class Predicate> struct count_t<Predicate> : std::integral_constant<size_t, 0> {};
struct all_of_t<P, T, Ts...> : conditional_t<P<T>::value, all_of_t<P, Ts...>, std::false_type> { }; template <template<typename> class Predicate, class T, class... Ts>
template <template<typename> class P, typename...> struct any_of_t : std::false_type { }; struct count_t<Predicate, T, Ts...> : std::integral_constant<size_t, Predicate<T>::value + count_t<Predicate, Ts...>::value> {};
template <template<typename> class P, typename T, typename... Ts>
struct any_of_t<P, T, Ts...> : conditional_t<P<T>::value, std::true_type, any_of_t<P, Ts...>> { };
#endif #endif
/// Return true if all/any Ts satify Predicate<T>
template <template<typename> class Predicate, typename... Ts>
using all_of_t = bool_constant<(count_t<Predicate, Ts...>::value == sizeof...(Ts))>;
template <template<typename> class Predicate, typename... Ts>
using any_of_t = bool_constant<(count_t<Predicate, Ts...>::value > 0)>;
// Extracts the first type from the template parameter pack matching the predicate, or Default if none match. // Extracts the first type from the template parameter pack matching the predicate, or Default if none match.
template <template<class> class Predicate, class Default, class... Ts> struct first_of; template <template<class> class Predicate, class Default, class... Ts> struct first_of;
template <template<class> class Predicate, class Default> struct first_of<Predicate, Default> { template <template<class> class Predicate, class Default> struct first_of<Predicate, Default> {
@ -373,13 +375,6 @@ struct first_of<Predicate, Default, T, Ts...> {
}; };
template <template<class> class Predicate, class Default, class... T> using first_of_t = typename first_of<Predicate, Default, T...>::type; template <template<class> class Predicate, class Default, class... T> using first_of_t = typename first_of<Predicate, Default, T...>::type;
// Counts the number of types in the template parameter pack matching the predicate
template <template<typename> class Predicate, typename... Ts> struct count_t;
template <template<typename> class Predicate> struct count_t<Predicate> : std::integral_constant<size_t, 0> {};
template <template<typename> class Predicate, class T, class... Ts>
struct count_t<Predicate, T, Ts...> : std::integral_constant<size_t,
Predicate<T>::value + count_t<Predicate, Ts...>::value> {};
/// Defer the evaluation of type T until types Us are instantiated /// Defer the evaluation of type T until types Us are instantiated
template <typename T, typename... /*Us*/> struct deferred_type { using type = T; }; template <typename T, typename... /*Us*/> struct deferred_type { using type = T; };
template <typename T, typename... Us> using deferred_t = typename deferred_type<T, Us...>::type; template <typename T, typename... Us> using deferred_t = typename deferred_type<T, Us...>::type;