X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=folly%2FApplyTuple.h;h=cce6fec07d6e3e23bf0e6a574f8ac352535953db;hb=d84e6482135417bafed3dea69c29b8d8b8c39970;hp=b22987766702fa4f023ae780abf30e0c55c7d4e9;hpb=74d1af87831f9df2b5cb9d104db1d0e2edab591e;p=folly.git

diff --git a/folly/ApplyTuple.h b/folly/ApplyTuple.h
index b2298776..cce6fec0 100644
--- a/folly/ApplyTuple.h
+++ b/folly/ApplyTuple.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 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.
@@ -31,6 +31,8 @@
 #include <tuple>
 #include <utility>
 
+#include <folly/Utility.h>
+
 namespace folly {
 
 //////////////////////////////////////////////////////////////////////
@@ -38,15 +40,6 @@ namespace folly {
 namespace detail {
 namespace apply_tuple {
 
-template <std::size_t...>
-struct IndexSequence {};
-
-template <std::size_t N, std::size_t... Is>
-struct MakeIndexSequence : MakeIndexSequence<N - 1, N - 1, Is...> {};
-
-template <std::size_t... Is>
-struct MakeIndexSequence<0, Is...> : IndexSequence<Is...> {};
-
 inline constexpr std::size_t sum() {
   return 0;
 }
@@ -61,7 +54,7 @@ struct TupleSizeSum {
 };
 
 template <typename... Tuples>
-using MakeIndexSequenceFromTuple = MakeIndexSequence<
+using MakeIndexSequenceFromTuple = folly::make_index_sequence<
     TupleSizeSum<typename std::decay<Tuples>::type...>::value>;
 
 // This is to allow using this with pointers to member functions,
@@ -76,14 +69,14 @@ inline constexpr auto makeCallable(M(C::*d)) -> decltype(std::mem_fn(d)) {
 }
 
 template <class F, class Tuple, std::size_t... Indexes>
-inline constexpr auto call(F&& f, Tuple&& t, IndexSequence<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, std::size_t... Indexes>
-inline constexpr auto forwardTuple(Tuple&& t, IndexSequence<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))...);
@@ -120,5 +113,52 @@ inline constexpr auto applyTuple(F&& f, Tuples&&... t)
       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
+
+/**
+ * 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));
+}
+
 //////////////////////////////////////////////////////////////////////
 }