1// Copyright (c) 2001-2020 Hartmut Kaiser
2//
3// Distributed under the Boost Software License, Version 1.0. (See accompanying
4// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
5
6#if !defined(BOOST_SPIRIT_KARMA_REAL_UTILS_FEB_23_2007_0841PM)
7#define BOOST_SPIRIT_KARMA_REAL_UTILS_FEB_23_2007_0841PM
8
9#if defined(_MSC_VER)
10#pragma once
11#endif
12
13#include <boost/config.hpp>
14#include <boost/config/no_tr1/cmath.hpp>
15#include <boost/detail/workaround.hpp>
16#include <boost/limits.hpp>
17
18#include <boost/spirit/home/support/char_class.hpp>
19#include <boost/spirit/home/support/unused.hpp>
20#include <boost/spirit/home/support/detail/pow10.hpp>
21#include <boost/spirit/home/karma/detail/generate_to.hpp>
22#include <boost/spirit/home/karma/detail/string_generate.hpp>
23#include <boost/spirit/home/karma/numeric/detail/numeric_utils.hpp>
24
25namespace boost { namespace spirit { namespace karma
26{
27 ///////////////////////////////////////////////////////////////////////////
28 //
29 // The real_inserter template takes care of the floating point number to
30 // string conversion. The Policies template parameter is used to allow
31 // customization of the formatting process
32 //
33 ///////////////////////////////////////////////////////////////////////////
34 template <typename T>
35 struct real_policies;
36
37 template <typename T
38 , typename Policies = real_policies<T>
39 , typename CharEncoding = unused_type
40 , typename Tag = unused_type>
41 struct real_inserter
42 {
43 template <typename OutputIterator, typename U>
44 static bool
45 call (OutputIterator& sink, U n, Policies const& p = Policies())
46 {
47 if (traits::test_nan(n)) {
48 return p.template nan<CharEncoding, Tag>(
49 sink, n, p.force_sign(n));
50 }
51 else if (traits::test_infinite(n)) {
52 return p.template inf<CharEncoding, Tag>(
53 sink, n, p.force_sign(n));
54 }
55 return p.template call<real_inserter>(sink, n, p);
56 }
57
58#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
59# pragma warning(push)
60# pragma warning(disable: 4100) // 'p': unreferenced formal parameter
61# pragma warning(disable: 4127) // conditional expression is constant
62# pragma warning(disable: 4267) // conversion from 'size_t' to 'unsigned int', possible loss of data
63#endif
64 ///////////////////////////////////////////////////////////////////////
65 // This is the workhorse behind the real generator
66 ///////////////////////////////////////////////////////////////////////
67 template <typename OutputIterator, typename U>
68 static bool
69 call_n (OutputIterator& sink, U n, Policies const& p)
70 {
71 // prepare sign and get output format
72 bool force_sign = p.force_sign(n);
73 bool sign_val = false;
74 int flags = p.floatfield(n);
75 if (traits::test_negative(n))
76 {
77 n = -n;
78 sign_val = true;
79 }
80
81 // The scientific representation requires the normalization of the
82 // value to convert.
83
84 // get correct precision for generated number
85 unsigned precision = p.precision(n);
86
87 // allow for ADL to find the correct overloads for log10 et.al.
88 using namespace std;
89
90 bool precexp_offset = false;
91 U dim = 0;
92 if (0 == (Policies::fmtflags::fixed & flags) && !traits::test_zero(n))
93 {
94 dim = log10(n);
95 if (dim > 0)
96 n /= spirit::traits::pow10<U>(traits::truncate_to_long::call(dim));
97 else if (n < 1.) {
98 long exp = traits::truncate_to_long::call(-dim);
99
100 dim = static_cast<U>(-exp);
101
102 // detect and handle denormalized numbers to prevent overflow in pow10
103 if (exp > std::numeric_limits<U>::max_exponent10)
104 {
105 n *= spirit::traits::pow10<U>(std::numeric_limits<U>::max_exponent10);
106 n *= spirit::traits::pow10<U>(exp - std::numeric_limits<U>::max_exponent10);
107 }
108 else
109 n *= spirit::traits::pow10<U>(exp);
110
111 if (n < 1.)
112 {
113 n *= 10.;
114 --dim;
115 precexp_offset = true;
116 }
117 }
118 }
119
120 // prepare numbers (sign, integer and fraction part)
121 U integer_part;
122 U precexp = spirit::traits::pow10<U>(precision);
123 U fractional_part = modf(n, &integer_part);
124
125 if (precexp_offset)
126 {
127 fractional_part =
128 floor((fractional_part * precexp + U(0.5)) * U(10.)) / U(10.);
129 }
130 else
131 {
132 fractional_part = floor(fractional_part * precexp + U(0.5));
133 }
134
135 if (fractional_part >= precexp)
136 {
137 fractional_part = floor(fractional_part - precexp);
138 integer_part += 1; // handle rounding overflow
139 if (integer_part >= 10. && 0 == (Policies::fmtflags::fixed & flags))
140 {
141 integer_part /= 10.;
142 ++dim;
143 }
144 }
145
146 // if trailing zeros are to be omitted, normalize the precision and``
147 // fractional part
148 U long_int_part = floor(integer_part);
149 U long_frac_part = fractional_part;
150 unsigned prec = precision;
151 if (!p.trailing_zeros(n))
152 {
153 U frac_part_floor = long_frac_part;
154 if (0 != long_frac_part) {
155 // remove the trailing zeros
156 while (0 != prec &&
157 0 == traits::remainder<10>::call(long_frac_part))
158 {
159 long_frac_part = traits::divide<10>::call(long_frac_part);
160 --prec;
161 }
162 }
163 else {
164 // if the fractional part is zero, we don't need to output
165 // any additional digits
166 prec = 0;
167 }
168
169 if (precision != prec)
170 {
171 long_frac_part = frac_part_floor /
172 spirit::traits::pow10<U>(precision-prec);
173 }
174 }
175
176 // call the actual generating functions to output the different parts
177 if ((force_sign || sign_val) &&
178 traits::test_zero(long_int_part) &&
179 traits::test_zero(long_frac_part))
180 {
181 sign_val = false; // result is zero, no sign please
182 force_sign = false;
183 }
184
185 // generate integer part
186 bool r = p.integer_part(sink, long_int_part, sign_val, force_sign);
187
188 // generate decimal point
189 r = r && p.dot(sink, long_frac_part, precision);
190
191 // generate fractional part with the desired precision
192 r = r && p.fraction_part(sink, long_frac_part, prec, precision);
193
194 if (r && 0 == (Policies::fmtflags::fixed & flags)) {
195 return p.template exponent<CharEncoding, Tag>(sink,
196 traits::truncate_to_long::call(dim));
197 }
198 return r;
199 }
200
201#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
202# pragma warning(pop)
203#endif
204
205 };
206}}}
207
208#endif
209
210

source code of boost/libs/spirit/include/boost/spirit/home/karma/numeric/detail/real_utils.hpp