1 //  Copyright John Maddock 2007.
2 //  Use, modification and distribution are subject to the
3 //  Boost Software License, Version 1.0. (See accompanying file
4 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
5 
6 #ifndef BOOST_MATH_ROUND_HPP
7 #define BOOST_MATH_ROUND_HPP
8 
9 #ifdef _MSC_VER
10 #pragma once
11 #endif
12 
13 #include <boost/math/tools/config.hpp>
14 #include <boost/math/policies/error_handling.hpp>
15 #include <boost/math/special_functions/math_fwd.hpp>
16 #include <boost/math/special_functions/fpclassify.hpp>
17 
18 namespace boost{ namespace math{
19 
20 namespace detail{
21 
22 template <class T, class Policy>
round(const T & v,const Policy & pol,const std::false_type &)23 inline typename tools::promote_args<T>::type round(const T& v, const Policy& pol, const std::false_type&)
24 {
25    BOOST_MATH_STD_USING
26       typedef typename tools::promote_args<T>::type result_type;
27    if(!(boost::math::isfinite)(v))
28       return policies::raise_rounding_error("boost::math::round<%1%>(%1%)", 0, static_cast<result_type>(v), static_cast<result_type>(v), pol);
29    //
30    // The logic here is rather convoluted, but avoids a number of traps,
31    // see discussion here https://github.com/boostorg/math/pull/8
32    //
33    if (-0.5 < v && v < 0.5)
34    {
35       // special case to avoid rounding error on the direct
36       // predecessor of +0.5 resp. the direct successor of -0.5 in
37       // IEEE floating point types
38       return static_cast<result_type>(0);
39    }
40    else if (v > 0)
41    {
42       // subtract v from ceil(v) first in order to avoid rounding
43       // errors on largest representable integer numbers
44       result_type c(ceil(v));
45       return 0.5 < c - v ? c - 1 : c;
46    }
47    else
48    {
49       // see former branch
50       result_type f(floor(v));
51       return 0.5 < v - f ? f + 1 : f;
52    }
53 }
54 template <class T, class Policy>
round(const T & v,const Policy &,const std::true_type &)55 inline typename tools::promote_args<T>::type round(const T& v, const Policy&, const std::true_type&)
56 {
57    return v;
58 }
59 
60 } // namespace detail
61 
62 template <class T, class Policy>
round(const T & v,const Policy & pol)63 inline typename tools::promote_args<T>::type round(const T& v, const Policy& pol)
64 {
65    return detail::round(v, pol, std::integral_constant<bool, detail::is_integer_for_rounding<T>::value>());
66 }
67 template <class T>
round(const T & v)68 inline typename tools::promote_args<T>::type round(const T& v)
69 {
70    return round(v, policies::policy<>());
71 }
72 //
73 // The following functions will not compile unless T has an
74 // implicit conversion to the integer types.  For user-defined
75 // number types this will likely not be the case.  In that case
76 // these functions should either be specialized for the UDT in
77 // question, or else overloads should be placed in the same
78 // namespace as the UDT: these will then be found via argument
79 // dependent lookup.  See our concept archetypes for examples.
80 //
81 // Non-standard numeric limits syntax "(std::numeric_limits<int>::max)()"
82 // is to avoid macro substiution from MSVC
83 // https://stackoverflow.com/questions/27442885/syntax-error-with-stdnumeric-limitsmax
84 //
85 template <class T, class Policy>
iround(const T & v,const Policy & pol)86 inline int iround(const T& v, const Policy& pol)
87 {
88    BOOST_MATH_STD_USING
89    typedef typename tools::promote_args<T>::type result_type;
90    T r = boost::math::round(v, pol);
91    if(r > static_cast<result_type>((std::numeric_limits<int>::max)()) || r < static_cast<result_type>((std::numeric_limits<int>::min)()))
92       return static_cast<int>(policies::raise_rounding_error("boost::math::iround<%1%>(%1%)", 0, v, 0, pol));
93    return static_cast<int>(r);
94 }
95 template <class T>
iround(const T & v)96 inline int iround(const T& v)
97 {
98    return iround(v, policies::policy<>());
99 }
100 
101 template <class T, class Policy>
lround(const T & v,const Policy & pol)102 inline long lround(const T& v, const Policy& pol)
103 {
104    BOOST_MATH_STD_USING
105    typedef typename tools::promote_args<T>::type result_type;
106    T r = boost::math::round(v, pol);
107    if(r > static_cast<result_type>((std::numeric_limits<long>::max)()) || r < static_cast<result_type>((std::numeric_limits<long>::min)()))
108       return static_cast<long int>(policies::raise_rounding_error("boost::math::lround<%1%>(%1%)", 0, v, 0L, pol));
109    return static_cast<long int>(r);
110 }
111 template <class T>
lround(const T & v)112 inline long lround(const T& v)
113 {
114    return lround(v, policies::policy<>());
115 }
116 
117 template <class T, class Policy>
llround(const T & v,const Policy & pol)118 inline long long llround(const T& v, const Policy& pol)
119 {
120    BOOST_MATH_STD_USING
121    typedef typename tools::promote_args<T>::type result_type;
122    T r = boost::math::round(v, pol);
123    if(r > static_cast<result_type>((std::numeric_limits<long long>::max)()) ||
124       r < static_cast<result_type>((std::numeric_limits<long long>::min)()))
125    {
126       return static_cast<long long>(policies::raise_rounding_error("boost::math::llround<%1%>(%1%)", 0, v, static_cast<long long>(0), pol));
127    }
128    return static_cast<long long>(r);
129 }
130 template <class T>
llround(const T & v)131 inline long long llround(const T& v)
132 {
133    return llround(v, policies::policy<>());
134 }
135 
136 }} // namespaces
137 
138 #endif // BOOST_MATH_ROUND_HPP
139