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1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#ifndef _LIBCPP___CXX03___RANDOM_GENERATE_CANONICAL_H
10#define _LIBCPP___CXX03___RANDOM_GENERATE_CANONICAL_H
11
12#include <__cxx03/__config>
13#include <__cxx03/__random/log2.h>
14#include <__cxx03/cstdint>
15#include <__cxx03/limits>
16
17#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
18# pragma GCC system_header
19#endif
20
21_LIBCPP_PUSH_MACROS
22#include <__cxx03/__undef_macros>
23
24_LIBCPP_BEGIN_NAMESPACE_STD
25
26// generate_canonical
27
28template <class _RealType, size_t __bits, class _URNG>
29_LIBCPP_HIDE_FROM_ABI _RealType generate_canonical(_URNG& __g) {
30 const size_t __dt = numeric_limits<_RealType>::digits;
31 const size_t __b = __dt < __bits ? __dt : __bits;
32 const size_t __log_r = __log2<uint64_t, _URNG::_Max - _URNG::_Min + uint64_t(1)>::value;
33 const size_t __k = __b / __log_r + (__b % __log_r != 0) + (__b == 0);
34 const _RealType __rp = static_cast<_RealType>(_URNG::max() - _URNG::min()) + _RealType(1);
35 _RealType __base = __rp;
36 _RealType __sp = __g() - _URNG::min();
37 for (size_t __i = 1; __i < __k; ++__i, __base *= __rp)
38 __sp += (__g() - _URNG::min()) * __base;
39 return __sp / __base;
40}
41
42_LIBCPP_END_NAMESPACE_STD
43
44_LIBCPP_POP_MACROS
45
46#endif // _LIBCPP___CXX03___RANDOM_GENERATE_CANONICAL_H
47

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source code of libcxx/include/__cxx03/__random/generate_canonical.h