/*
- * Copyright 2014 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* ASSERT(x == 24);
*/
-#ifndef FOLLY_APPLYTUPLE_H_
-#define FOLLY_APPLYTUPLE_H_
+#pragma once
-#include <tuple>
#include <functional>
-#include <type_traits>
+#include <tuple>
+#include <utility>
+
+#include <folly/Utility.h>
namespace folly {
//////////////////////////////////////////////////////////////////////
namespace detail {
+namespace apply_tuple {
+
+inline constexpr std::size_t sum() {
+ return 0;
+}
+template <typename... Args>
+inline constexpr std::size_t sum(std::size_t v1, Args... vs) {
+ return v1 + sum(vs...);
+}
+
+template <typename... Tuples>
+struct TupleSizeSum {
+ static constexpr auto value = sum(std::tuple_size<Tuples>::value...);
+};
+
+template <typename... Tuples>
+using MakeIndexSequenceFromTuple = folly::make_index_sequence<
+ TupleSizeSum<typename std::decay<Tuples>::type...>::value>;
// This is to allow using this with pointers to member functions,
// where the first argument in the tuple will be the this pointer.
-template<class F> F& makeCallable(F& f) { return f; }
-template<class R, class C, class ...A>
-auto makeCallable(R (C::*d)(A...)) -> decltype(std::mem_fn(d)) {
+template <class F>
+inline constexpr F&& makeCallable(F&& f) {
+ return std::forward<F>(f);
+}
+template <class M, class C>
+inline constexpr auto makeCallable(M(C::*d)) -> decltype(std::mem_fn(d)) {
return std::mem_fn(d);
}
-template<class Tuple>
-struct DerefSize
- : std::tuple_size<typename std::remove_reference<Tuple>::type>
-{};
-
-template<class Tuple, class ...Unpacked> struct ExprDoUnpack {
- enum {
- value = sizeof...(Unpacked) < DerefSize<Tuple>::value
- };
-};
+template <class F, class Tuple, std::size_t... Indexes>
+inline constexpr auto call(F&& f, Tuple&& t, folly::index_sequence<Indexes...>)
+ -> decltype(
+ std::forward<F>(f)(std::get<Indexes>(std::forward<Tuple>(t))...)) {
+ return std::forward<F>(f)(std::get<Indexes>(std::forward<Tuple>(t))...);
+}
-template<class Tuple, class ...Unpacked> struct ExprIsUnpacked {
- enum {
- value = sizeof...(Unpacked) == DerefSize<Tuple>::value
- };
-};
+template <class Tuple, std::size_t... Indexes>
+inline constexpr auto forwardTuple(Tuple&& t, folly::index_sequence<Indexes...>)
+ -> decltype(
+ std::forward_as_tuple(std::get<Indexes>(std::forward<Tuple>(t))...)) {
+ return std::forward_as_tuple(std::get<Indexes>(std::forward<Tuple>(t))...);
+}
-// CallTuple recursively unpacks tuple arguments so we can forward
-// them into the function.
-template<class Ret>
-struct CallTuple {
- template<class F, class Tuple, class ...Unpacked>
- static typename std::enable_if<ExprDoUnpack<Tuple, Unpacked...>::value,
- Ret
- >::type call(const F& f, Tuple&& t, Unpacked&&... unp) {
- typedef typename std::tuple_element<
- sizeof...(Unpacked),
- typename std::remove_reference<Tuple>::type
- >::type ElementType;
- return CallTuple<Ret>::call(f, std::forward<Tuple>(t),
- std::forward<Unpacked>(unp)...,
- std::forward<ElementType>(std::get<sizeof...(Unpacked)>(t))
- );
- }
+} // namespace apply_tuple
+} // namespace detail
- template<class F, class Tuple, class ...Unpacked>
- static typename std::enable_if<ExprIsUnpacked<Tuple, Unpacked...>::value,
- Ret
- >::type call(const F& f, Tuple&& t, Unpacked&&... unp) {
- return makeCallable(f)(std::forward<Unpacked>(unp)...);
- }
-};
+//////////////////////////////////////////////////////////////////////
-// The point of this meta function is to extract the contents of the
-// tuple as a parameter pack so we can pass it into std::result_of<>.
-template<class F, class Args> struct ReturnValue {};
-template<class F, class ...Args>
-struct ReturnValue<F,std::tuple<Args...>> {
- typedef typename std::result_of<F (Args...)>::type type;
-};
+/**
+ * Invoke a callable object with a set of arguments passed as a tuple, or a
+ * series of tuples
+ *
+ * Example: the following lines are equivalent
+ * func(1, 2, 3, "foo");
+ * applyTuple(func, std::make_tuple(1, 2, 3, "foo"));
+ * applyTuple(func, std::make_tuple(1, 2), std::make_tuple(3, "foo"));
+ */
+template <class F, class... Tuples>
+inline constexpr auto applyTuple(F&& f, Tuples&&... t)
+ -> decltype(detail::apply_tuple::call(
+ detail::apply_tuple::makeCallable(std::forward<F>(f)),
+ std::tuple_cat(detail::apply_tuple::forwardTuple(
+ std::forward<Tuples>(t),
+ detail::apply_tuple::MakeIndexSequenceFromTuple<Tuples>{})...),
+ detail::apply_tuple::MakeIndexSequenceFromTuple<Tuples...>{})) {
+ return detail::apply_tuple::call(
+ detail::apply_tuple::makeCallable(std::forward<F>(f)),
+ std::tuple_cat(detail::apply_tuple::forwardTuple(
+ std::forward<Tuples>(t),
+ detail::apply_tuple::MakeIndexSequenceFromTuple<Tuples>{})...),
+ detail::apply_tuple::MakeIndexSequenceFromTuple<Tuples...>{});
}
-//////////////////////////////////////////////////////////////////////
+namespace detail {
+namespace apply_tuple {
+
+template <class F>
+class Uncurry {
+ public:
+ explicit Uncurry(F&& func) : func_(std::move(func)) {}
+ explicit Uncurry(const F& func) : func_(func) {}
+
+ template <class Tuple>
+ auto operator()(Tuple&& tuple) const
+ -> decltype(applyTuple(std::declval<F>(), std::forward<Tuple>(tuple))) {
+ return applyTuple(func_, std::forward<Tuple>(tuple));
+ }
+
+ private:
+ F func_;
+};
+} // namespace apply_tuple
+} // namespace detail
-template<class Callable, class Tuple>
-typename detail::ReturnValue<
- typename std::decay<Callable>::type,
- typename std::remove_reference<Tuple>::type
->::type
-applyTuple(const Callable& c, Tuple&& t) {
- typedef typename detail::ReturnValue<
- typename std::decay<Callable>::type,
- typename std::remove_reference<Tuple>::type
- >::type RetT;
- return detail::CallTuple<RetT>::call(c, std::forward<Tuple>(t));
+/**
+ * Wraps a function taking N arguments into a function which accepts a tuple of
+ * N arguments. Note: This function will also accept an std::pair if N == 2.
+ *
+ * For example, given the below code:
+ *
+ * std::vector<std::tuple<int, int, int>> rows = ...;
+ * auto test = [](std::tuple<int, int, int>& row) {
+ * return std::get<0>(row) * std::get<1>(row) * std::get<2>(row) == 24;
+ * };
+ * auto found = std::find_if(rows.begin(), rows.end(), test);
+ *
+ *
+ * 'test' could be rewritten as:
+ *
+ * auto test =
+ * folly::uncurry([](int a, int b, int c) { return a * b * c == 24; });
+ *
+ */
+template <class F>
+auto uncurry(F&& f)
+ -> detail::apply_tuple::Uncurry<typename std::decay<F>::type> {
+ return detail::apply_tuple::Uncurry<typename std::decay<F>::type>(
+ std::forward<F>(f));
}
//////////////////////////////////////////////////////////////////////
-
}
-
-#endif
projects / folly.git / blobdiff