1 //===----------------------------------------------------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is dual licensed under the MIT and the University of Illinois Open
6 // Source Licenses. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9
10 // <random>
11
12 // template<class RealType = double>
13 // class cauchy_distribution
14
15 // template<class _URNG> result_type operator()(_URNG& g);
16
17 #include <random>
18 #include <cassert>
19 #include <vector>
20 #include <algorithm>
21
22 double
f(double x,double a,double b)23 f(double x, double a, double b)
24 {
25 return 1/3.1415926535897932 * std::atan((x - a)/b) + .5;
26 }
27
main()28 int main()
29 {
30 {
31 typedef std::cauchy_distribution<> D;
32 typedef D::param_type P;
33 typedef std::mt19937 G;
34 G g;
35 const double a = 10;
36 const double b = .5;
37 D d(a, b);
38 const int N = 1000000;
39 std::vector<D::result_type> u;
40 for (int i = 0; i < N; ++i)
41 u.push_back(d(g));
42 std::sort(u.begin(), u.end());
43 for (int i = 0; i < N; ++i)
44 assert(std::abs(f(u[i], a, b) - double(i)/N) < .001);
45 }
46 {
47 typedef std::cauchy_distribution<> D;
48 typedef D::param_type P;
49 typedef std::mt19937 G;
50 G g;
51 const double a = -1.5;
52 const double b = 1;
53 D d(a, b);
54 const int N = 1000000;
55 std::vector<D::result_type> u;
56 for (int i = 0; i < N; ++i)
57 u.push_back(d(g));
58 std::sort(u.begin(), u.end());
59 for (int i = 0; i < N; ++i)
60 assert(std::abs(f(u[i], a, b) - double(i)/N) < .001);
61 }
62 {
63 typedef std::cauchy_distribution<> D;
64 typedef D::param_type P;
65 typedef std::mt19937 G;
66 G g;
67 const double a = .5;
68 const double b = 2;
69 D d(a, b);
70 const int N = 1000000;
71 std::vector<D::result_type> u;
72 for (int i = 0; i < N; ++i)
73 u.push_back(d(g));
74 std::sort(u.begin(), u.end());
75 for (int i = 0; i < N; ++i)
76 assert(std::abs(f(u[i], a, b) - double(i)/N) < .001);
77 }
78 }
79