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refine the implementation of has_find type_traits (#319)

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* refine the implementation of has_find type_traits

* Format fix
This commit is contained in:
fpeng1985 2019-09-19 02:24:24 +08:00 committed by Henry Schreiner
parent b029b325b5
commit 09c169c2d9
1 changed files with 7 additions and 7 deletions
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14
include/CLI/Validators.hpp
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@ -501,14 +501,14 @@ template <typename T> std::string generate_map(const T &map, bool key_only = fal
return out;
}
template <typename> struct sfinae_true : std::true_type {};
/// Function to check for the existence of a member find function which presumably is more efficient than looping over
/// everything
template <typename T, typename V>
static auto test_find(int) -> sfinae_true<decltype(std::declval<T>().find(std::declval<V>()))>;
template <typename, typename V> static auto test_find(long) -> std::false_type;
template <typename C, typename V> struct has_find {
template <typename CC, typename VV>
static auto test(int) -> decltype(std::declval<CC>().find(std::declval<VV>()), std::true_type());
template <typename, typename> static auto test(...) -> decltype(std::false_type());
template <typename T, typename V> struct has_find : decltype(test_find<T, V>(0)) {};
static const auto value = decltype(test<C, V>(0))::value;
using type = std::integral_constant<bool, value>;
};
/// A search function
template <typename T, typename V, enable_if_t<!has_find<T, V>::value, detail::enabler> = detail::dummy>