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author | 2018-01-17 09:53:47 -0800 | |
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committer | 2018-01-17 18:56:51 -0500 | |
commit | 5a8de8a37e3e282d22f69ca67b4aba8e4cca63ae (patch) | |
tree | f65088aad40e74c0959db9b313b30f59514f7467 /absl/utility/utility.h | |
parent | be40fdf1a86f4956d2f8125a7b6bd6d34e133c2d (diff) |
Changes imported from Abseil "staging" branch:
- 5e874e644191fbf99f5636d6303de2b28b23392c Adds a absl::apply function, similar to c++17's std::apply. by Abseil Team <absl-team@google.com>
- 16373c438d16a09725dace03ab7ba0f7c2337279 Add debugging_internal::StackTraceWorksForTest by Abseil Team <absl-team@google.com>
- a623257aaaff8a5fba3377f34f92f319a104e444 Update absl::CondVar documentation in response to GitHub ... by Derek Mauro <dmauro@google.com>
- 87d58a25bc4ecd46165dd1c417121c86cbc07be0 Add assert against uint128 negative bit shift undefined b... by Alex Strelnikov <strel@google.com>
- af155c0d2a3556b56a9bcd6f9ee7416277185df8 Fix comment typos. by Abseil Team <absl-team@google.com>
- 1824ae832eb75d447dea730b5968d952897e135a Rollback of: Add debugging_internal::StackTraceWorksForTest by Abseil Team <absl-team@google.com>
- 97318f087ce63dd5acf1e0d3d697cd90a7d6ebfd Add debugging_internal::StackTraceWorksForTest by Abseil Team <absl-team@google.com>
- 9dd1d17dca17f0ded3bda336b7521fd57d08a5cc Move log_severity.h out of internal. by Abseil Team <absl-team@google.com>
- 2212bb56b1a8365d2303ff0983441298d08444e5 Internal change. by Alex Strelnikov <strel@google.com>
GitOrigin-RevId: 5e874e644191fbf99f5636d6303de2b28b23392c
Change-Id: Ic270393ac1f15866afb64617d28269cd829030f6
Diffstat (limited to 'absl/utility/utility.h')
-rw-r--r-- | absl/utility/utility.h | 79 |
1 files changed, 61 insertions, 18 deletions
diff --git a/absl/utility/utility.h b/absl/utility/utility.h index 732cd4c5..d37f4c30 100644 --- a/absl/utility/utility.h +++ b/absl/utility/utility.h @@ -23,6 +23,7 @@ // * make_integer_sequence<T, N> == std::make_integer_sequence<T, N> // * make_index_sequence<N> == std::make_index_sequence<N> // * index_sequence_for<Ts...> == std::index_sequence_for<Ts...> +// * apply<Functor, Tuple> == std::apply<Functor, Tuple> // // This header file also provides the tag types `in_place_t`, `in_place_type_t`, // and `in_place_index_t`, as well as the constant `in_place`, and @@ -31,34 +32,20 @@ // References: // // http://en.cppreference.com/w/cpp/utility/integer_sequence +// http://en.cppreference.com/w/cpp/utility/apply // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3658.html // -// -// Example: -// // Unpack a tuple for use as a function call's argument list. -// -// template <typename F, typename Tup, size_t... Is> -// auto Impl(F f, const Tup& tup, absl::index_sequence<Is...>) -// -> decltype(f(std::get<Is>(tup) ...)) { -// return f(std::get<Is>(tup) ...); -// } -// -// template <typename Tup> -// using TupIdxSeq = absl::make_index_sequence<std::tuple_size<Tup>::value>; -// -// template <typename F, typename Tup> -// auto ApplyFromTuple(F f, const Tup& tup) -// -> decltype(Impl(f, tup, TupIdxSeq<Tup>{})) { -// return Impl(f, tup, TupIdxSeq<Tup>{}); -// } + #ifndef ABSL_UTILITY_UTILITY_H_ #define ABSL_UTILITY_UTILITY_H_ #include <cstddef> #include <cstdlib> +#include <tuple> #include <utility> #include "absl/base/config.h" +#include "absl/base/internal/invoke.h" #include "absl/meta/type_traits.h" namespace absl { @@ -214,6 +201,62 @@ constexpr T&& forward( return static_cast<T&&>(t); } +namespace utility_internal { +// Helper method for expanding tuple into a called method. +template <typename Functor, typename Tuple, std::size_t... Indexes> +auto apply_helper(Functor&& functor, Tuple&& t, index_sequence<Indexes...>) + -> decltype(absl::base_internal::Invoke( + absl::forward<Functor>(functor), + std::get<Indexes>(absl::forward<Tuple>(t))...)) { + return absl::base_internal::Invoke( + absl::forward<Functor>(functor), + std::get<Indexes>(absl::forward<Tuple>(t))...); +} + +} // namespace utility_internal + +// apply +// +// Invokes a Callable using elements of a tuple as its arguments. +// Each element of the tuple corresponds to an argument of the call (in order). +// Both the Callable argument and the tuple argument are perfect-forwarded. +// For member-function Callables, the first tuple element acts as the `this` +// pointer. `absl::apply` is designed to be a drop-in replacement for C++17's +// `std::apply`. Unlike C++17's `std::apply`, this is not currently `constexpr`. +// +// Example: +// +// class Foo{void Bar(int);}; +// void user_function(int, std::string); +// void user_function(std::unique_ptr<Foo>); +// +// int main() +// { +// std::tuple<int, std::string> tuple1(42, "bar"); +// // Invokes the user function overload on int, std::string. +// absl::apply(&user_function, tuple1); +// +// auto foo = absl::make_unique<Foo>(); +// std::tuple<Foo*, int> tuple2(foo.get(), 42); +// // Invokes the method Bar on foo with one argument 42. +// absl::apply(&Foo::Bar, foo.get(), 42); +// +// std::tuple<std::unique_ptr<Foo>> tuple3(absl::make_unique<Foo>()); +// // Invokes the user function that takes ownership of the unique +// // pointer. +// absl::apply(&user_function, std::move(tuple)); +// } +template <typename Functor, typename Tuple> +auto apply(Functor&& functor, Tuple&& t) + -> decltype(utility_internal::apply_helper( + absl::forward<Functor>(functor), absl::forward<Tuple>(t), + absl::make_index_sequence<std::tuple_size< + typename std::remove_reference<Tuple>::type>::value>{})) { + return utility_internal::apply_helper( + absl::forward<Functor>(functor), absl::forward<Tuple>(t), + absl::make_index_sequence<std::tuple_size< + typename std::remove_reference<Tuple>::type>::value>{}); +} } // namespace absl #endif // ABSL_UTILITY_UTILITY_H_ |