1 /* Copyright (c) 2016-2018. The SimGrid Team.
2 * All rights reserved. */
4 /* This program is free software; you can redistribute it and/or modify it
5 * under the terms of the license (GNU LGPL) which comes with this package. */
7 #ifndef XBT_UTILITY_HPP
8 #define XBT_UTILITY_HPP
15 /** @brief Comparator class for using with std::priority_queue or boost::heap.
17 * Compare two std::pair by their first element (of type double), and return true when the first is greater than the
18 * second. Useful to have priority queues with the smallest element on top.
20 template <class Pair> class HeapComparator {
22 bool operator()(const Pair& a, const Pair& b) const { return a.first > b.first; }
25 /** @brief Erase an element given by reference from a boost::intrusive::list.
27 template <class List, class Elem> inline void intrusive_erase(List& list, Elem& elem)
29 list.erase(list.iterator_to(elem));
32 // integer_sequence and friends from C++14
33 // We need them to implement `apply` from C++17.
35 /** A compile-time sequence of integers (from C++14)
37 * `index_sequence<std::size_t,1,5,7,9>` represents the sequence `(1,5,7,9)`.
40 * template<class T, std::size_t... I>
41 * auto extract_tuple(T&& t, integer_sequence<std::size_t, I...>)
42 * -> decltype(std::make_tuple(std::get<I>(std::forward<T>(t))...))
44 * return std::make_tuple(std::get<I>(std::forward<T>(t))...);
49 * integer_sequence<std::size_t, 1, 3> seq;
50 * auto a = std::make_tuple(1, 2.0, false, 'a');
51 * auto b = extract_tuple(a, seq);
52 * std::cout << std::get<0>(b) << '\n'; // 2
53 * std::cout << std::get<1>(b) << '\n'; // a
58 template<class T, T... N>
59 class integer_sequence {
60 static constexpr std::size_t size()
62 return std::tuple_size<decltype(std::make_tuple(N...))>::value;
67 template<class T, long long N, long long... M>
68 struct make_integer_sequence :
69 make_integer_sequence<T, N-1, N-1, M...>
71 template<class T, long long... M>
72 struct make_integer_sequence<T, 0, M...> {
73 typedef integer_sequence<T, (T) M...> type;
77 /** A compile-time sequence of integers of the form `(0,1,2,3,...,N-1)` (from C++14) */
78 template<class T, T N>
79 using make_integer_sequence = typename simgrid::xbt::bits::make_integer_sequence<T,N>::type;
81 /** A compile-time sequence of indices (from C++14) */
82 template<std::size_t... Ints>
83 using index_sequence = integer_sequence<std::size_t, Ints...>;
85 /** A compile-time sequence of indices of the form `(0,1,2,3,...,N-1)` (from C++14) */
86 template<std::size_t N>
87 using make_index_sequence = make_integer_sequence<std::size_t, N>;
89 /** Convert a type parameter pack into a index_sequence (from C++14) */
91 using index_sequence_for = make_index_sequence<sizeof...(T)>;
93 static_assert(std::is_same< make_index_sequence<0>, index_sequence<> >::value, "seq0");
94 static_assert(std::is_same< make_index_sequence<1>, index_sequence<0> >::value, "seq1");
95 static_assert(std::is_same< make_index_sequence<2>, index_sequence<0, 1> >::value, "seq2");
96 static_assert(std::is_same< make_index_sequence<3>, index_sequence<0, 1, 2> >::value, "seq3");
97 static_assert(std::is_same< index_sequence_for<int,double,float>, make_index_sequence<3> >::value, "seq4");