1 // Copyright 2019 Hans Dembinski
2 //
3 // Distributed under the Boost Software License, Version 1.0.
4 // (See accompanying file LICENSE_1_0.txt
5 // or copy at http://www.boost.org/LICENSE_1_0.txt)
6
7 #include <array>
8 #include <random>
9
10 using uniform = std::uniform_real_distribution<>;
11 using uniform_int = std::uniform_int_distribution<>;
12 using normal = std::normal_distribution<>;
13
14 template <class Distribution, class... Ts>
15 Distribution init(Ts...);
16
17 template <>
init()18 uniform init<uniform>() {
19 return uniform{0.0, 1.0};
20 }
21
22 template <>
init()23 normal init<normal>() {
24 return normal{0.5, 0.3};
25 }
26
27 template <>
init(int n)28 uniform_int init<uniform_int, int>(int n) {
29 return uniform_int{0, n};
30 }
31
32 template <class Distribution, std::size_t N = 1 << 15>
33 struct generator : std::array<double, N> {
34 using base_t = std::array<double, N>;
35
36 template <class... Ts>
generatorgenerator37 generator(Ts... ts) {
38 std::default_random_engine rng(1);
39 auto dis = init<Distribution>(ts...);
40 std::generate(base_t::begin(), base_t::end(), [&] { return dis(rng); });
41 }
42
operator ()generator43 const double& operator()() {
44 ++ptr_;
45 if (ptr_ == base_t::data() + N) ptr_ = base_t::data();
46 return *ptr_;
47 }
48
49 const double* ptr_ = base_t::data() - 1;
50 };
51