1 // Copyright Kevlin Henney, 2000-2005.
2 // Copyright Alexander Nasonov, 2006-2010.
3 // Copyright Antony Polukhin, 2011-2014.
5 // Distributed under the Boost Software License, Version 1.0. (See
6 // accompanying file LICENSE_1_0.txt or copy at
7 // http://www.boost.org/LICENSE_1_0.txt)
9 // what: lexical_cast custom keyword cast
10 // who: contributed by Kevlin Henney,
11 // enhanced with contributions from Terje Slettebo,
12 // with additional fixes and suggestions from Gennaro Prota,
13 // Beman Dawes, Dave Abrahams, Daryle Walker, Peter Dimov,
14 // Alexander Nasonov, Antony Polukhin, Justin Viiret, Michael Hofmann,
15 // Cheng Yang, Matthew Bradbury, David W. Birdsall, Pavel Korzh and other Boosters
16 // when: November 2000, March 2003, June 2005, June 2006, March 2011 - 2014
18 #ifndef BOOST_LEXICAL_CAST_DETAIL_CONVERTER_NUMERIC_HPP
19 #define BOOST_LEXICAL_CAST_DETAIL_CONVERTER_NUMERIC_HPP
21 #include <boost/config.hpp>
22 #ifdef BOOST_HAS_PRAGMA_ONCE
26 #include <boost/limits.hpp>
27 #include <boost/mpl/eval_if.hpp>
28 #include <boost/mpl/identity.hpp>
29 #include <boost/mpl/if.hpp>
30 #include <boost/type_traits/make_unsigned.hpp>
31 #include <boost/type_traits/is_signed.hpp>
32 #include <boost/type_traits/is_integral.hpp>
33 #include <boost/type_traits/is_arithmetic.hpp>
34 #include <boost/type_traits/is_base_of.hpp>
35 #include <boost/type_traits/is_float.hpp>
37 #include <boost/numeric/conversion/cast.hpp>
39 namespace boost { namespace detail {
41 template <class Source >
42 struct detect_precision_loss
44 typedef Source source_type;
45 typedef boost::numeric::Trunc<Source> Rounder;
46 typedef BOOST_DEDUCED_TYPENAME mpl::if_<
47 boost::is_arithmetic<Source>, Source, Source const&
48 >::type argument_type ;
50 static inline source_type nearbyint(argument_type s, bool& is_ok) BOOST_NOEXCEPT {
51 const source_type near_int = Rounder::nearbyint(s);
52 if (near_int && is_ok) {
53 const source_type orig_div_round = s / near_int;
54 const source_type eps = std::numeric_limits<source_type>::epsilon();
56 is_ok = !((orig_div_round > 1 ? orig_div_round - 1 : 1 - orig_div_round) > eps);
62 typedef typename Rounder::round_style round_style;
65 template <typename Base, class Source>
66 struct fake_precision_loss: public Base
68 typedef Source source_type ;
69 typedef BOOST_DEDUCED_TYPENAME mpl::if_<
70 boost::is_arithmetic<Source>, Source, Source const&
71 >::type argument_type ;
73 static inline source_type nearbyint(argument_type s, bool& /*is_ok*/) BOOST_NOEXCEPT {
78 struct nothrow_overflow_handler
80 inline bool operator() ( boost::numeric::range_check_result r ) const BOOST_NOEXCEPT {
81 return (r == boost::numeric::cInRange);
85 template <typename Target, typename Source>
86 inline bool noexcept_numeric_convert(const Source& arg, Target& result) BOOST_NOEXCEPT {
87 typedef boost::numeric::converter<
90 boost::numeric::conversion_traits<Target, Source >,
91 nothrow_overflow_handler,
92 detect_precision_loss<Source >
95 typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_c<
96 boost::is_base_of< detect_precision_loss<Source >, converter_orig_t >::value,
98 fake_precision_loss<converter_orig_t, Source>
101 bool res = nothrow_overflow_handler()(converter_t::out_of_range(arg));
102 result = converter_t::low_level_convert(converter_t::nearbyint(arg, res));
106 template <typename Target, typename Source>
107 struct lexical_cast_dynamic_num_not_ignoring_minus
109 static inline bool try_convert(const Source &arg, Target& result) BOOST_NOEXCEPT {
110 return noexcept_numeric_convert<Target, Source >(arg, result);
114 template <typename Target, typename Source>
115 struct lexical_cast_dynamic_num_ignoring_minus
117 static inline bool try_convert(const Source &arg, Target& result) BOOST_NOEXCEPT {
118 typedef BOOST_DEDUCED_TYPENAME boost::mpl::eval_if_c<
119 boost::is_float<Source>::value,
120 boost::mpl::identity<Source>,
121 boost::make_unsigned<Source>
125 const bool res = noexcept_numeric_convert<Target, usource_t>(0u - arg, result);
126 result = static_cast<Target>(0u - result);
129 return noexcept_numeric_convert<Target, usource_t>(arg, result);
135 * lexical_cast_dynamic_num follows the rules:
136 * 1) If Source can be converted to Target without precision loss and
137 * without overflows, then assign Source to Target and return
139 * 2) If Source is less than 0 and Target is an unsigned integer,
140 * then negate Source, check the requirements of rule 1) and if
141 * successful, assign static_casted Source to Target and return
143 * 3) Otherwise throw a bad_lexical_cast exception
146 * Rule 2) required because boost::lexical_cast has the behavior of
147 * stringstream, which uses the rules of scanf for conversions. And
148 * in the C99 standard for unsigned input value minus sign is
149 * optional, so if a negative number is read, no errors will arise
150 * and the result will be the two's complement.
152 template <typename Target, typename Source>
153 struct dynamic_num_converter_impl
155 static inline bool try_convert(const Source &arg, Target& result) BOOST_NOEXCEPT {
156 typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_c<
157 boost::is_unsigned<Target>::value &&
158 (boost::is_signed<Source>::value || boost::is_float<Source>::value) &&
159 !(boost::is_same<Source, bool>::value) &&
160 !(boost::is_same<Target, bool>::value),
161 lexical_cast_dynamic_num_ignoring_minus<Target, Source>,
162 lexical_cast_dynamic_num_not_ignoring_minus<Target, Source>
167 typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_<
168 BOOST_DEDUCED_TYPENAME boost::mpl::and_<
169 boost::is_unsigned<Target>,
171 boost::is_signed<Source>,
172 boost::is_float<Source>
175 boost::is_same<Source, bool>
178 boost::is_same<Target, bool>
181 lexical_cast_dynamic_num_ignoring_minus<Target, Source>,
182 lexical_cast_dynamic_num_not_ignoring_minus<Target, Source>
187 return caster_type::try_convert(arg, result);
191 }} // namespace boost::detail
193 #endif // BOOST_LEXICAL_CAST_DETAIL_CONVERTER_NUMERIC_HPP