/Src/Dependencies/Boost/boost/spirit/home/karma/numeric/real_policies.hpp
C++ Header | 333 lines | 109 code | 24 blank | 200 comment | 9 complexity | 7f69719e409cf59715c2ef103f8bfad7 MD5 | raw file
1// Copyright (c) 2001-2011 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_POLICIES_MAR_02_2007_0936AM) 7#define BOOST_SPIRIT_KARMA_REAL_POLICIES_MAR_02_2007_0936AM 8 9#if defined(_MSC_VER) 10#pragma once 11#endif 12 13#include <boost/config/no_tr1/cmath.hpp> 14#include <boost/math/special_functions/fpclassify.hpp> 15#include <boost/type_traits/remove_const.hpp> 16 17#include <boost/spirit/home/support/char_class.hpp> 18#include <boost/spirit/home/karma/generator.hpp> 19#include <boost/spirit/home/karma/char.hpp> 20#include <boost/spirit/home/karma/numeric/int.hpp> 21#include <boost/spirit/home/karma/numeric/detail/real_utils.hpp> 22 23#include <boost/mpl/bool.hpp> 24 25namespace boost { namespace spirit { namespace karma 26{ 27 /////////////////////////////////////////////////////////////////////////// 28 // 29 // real_policies, if you need special handling of your floating 30 // point numbers, just overload this policy class and use it as a template 31 // parameter to the karma::real_generator floating point specifier: 32 // 33 // template <typename T> 34 // struct scientific_policy : karma::real_policies<T> 35 // { 36 // // we want the numbers always to be in scientific format 37 // static int floatfield(T n) { return fmtflags::scientific; } 38 // }; 39 // 40 // typedef 41 // karma::real_generator<double, scientific_policy<double> > 42 // science_type; 43 // 44 // karma::generate(sink, science_type(), 1.0); // will output: 1.0e00 45 // 46 /////////////////////////////////////////////////////////////////////////// 47 template <typename T> 48 struct real_policies 49 { 50 /////////////////////////////////////////////////////////////////////// 51 // Expose the data type the generator is targeted at 52 /////////////////////////////////////////////////////////////////////// 53 typedef T value_type; 54 55 /////////////////////////////////////////////////////////////////////// 56 // By default the policy doesn't require any special iterator 57 // functionality. The floating point generator exposes its properties 58 // from here, so this needs to be updated in case other properties 59 // need to be implemented. 60 /////////////////////////////////////////////////////////////////////// 61 typedef mpl::int_<generator_properties::no_properties> properties; 62 63 /////////////////////////////////////////////////////////////////////// 64 // Specifies, which representation type to use during output 65 // generation. 66 /////////////////////////////////////////////////////////////////////// 67 struct fmtflags 68 { 69 enum { 70 scientific = 0, // Generate floating-point values in scientific 71 // format (with an exponent field). 72 fixed = 1 // Generate floating-point values in fixed-point 73 // format (with no exponent field). 74 }; 75 }; 76 77 /////////////////////////////////////////////////////////////////////// 78 // This is the main function used to generate the output for a 79 // floating point number. It is called by the real generator in order 80 // to perform the conversion. In theory all of the work can be 81 // implemented here, but it is the easiest to use existing 82 // functionality provided by the type specified by the template 83 // parameter `Inserter`. 84 // 85 // sink: the output iterator to use for generation 86 // n: the floating point number to convert 87 // p: the instance of the policy type used to instantiate this 88 // floating point generator. 89 /////////////////////////////////////////////////////////////////////// 90 template <typename Inserter, typename OutputIterator, typename Policies> 91 static bool 92 call (OutputIterator& sink, T n, Policies const& p) 93 { 94 return Inserter::call_n(sink, n, p); 95 } 96 97 /////////////////////////////////////////////////////////////////////// 98 // The default behavior is to not to require generating a sign. If 99 // 'force_sign()' returns true, then all generated numbers will 100 // have a sign ('+' or '-', zeros will have a space instead of a sign) 101 // 102 // n The floating point number to output. This can be used to 103 // adjust the required behavior depending on the value of 104 // this number. 105 /////////////////////////////////////////////////////////////////////// 106 static bool force_sign(T) 107 { 108 return false; 109 } 110 111 /////////////////////////////////////////////////////////////////////// 112 // Return whether trailing zero digits have to be emitted in the 113 // fractional part of the output. If set, this flag instructs the 114 // floating point generator to emit trailing zeros up to the required 115 // precision digits (as returned by the precision() function). 116 // 117 // n The floating point number to output. This can be used to 118 // adjust the required behavior depending on the value of 119 // this number. 120 /////////////////////////////////////////////////////////////////////// 121 static bool trailing_zeros(T) 122 { 123 // the default behavior is not to generate trailing zeros 124 return false; 125 } 126 127 /////////////////////////////////////////////////////////////////////// 128 // Decide, which representation type to use in the generated output. 129 // 130 // By default all numbers having an absolute value of zero or in 131 // between 0.001 and 100000 will be generated using the fixed format, 132 // all others will be generated using the scientific representation. 133 // 134 // The function trailing_zeros() can be used to force the output of 135 // trailing zeros in the fractional part up to the number of digits 136 // returned by the precision() member function. The default is not to 137 // generate the trailing zeros. 138 // 139 // n The floating point number to output. This can be used to 140 // adjust the formatting flags depending on the value of 141 // this number. 142 /////////////////////////////////////////////////////////////////////// 143 static int floatfield(T n) 144 { 145 if (traits::test_zero(n)) 146 return fmtflags::fixed; 147 148 T abs_n = traits::get_absolute_value(n); 149 return (abs_n >= 1e5 || abs_n < 1e-3) 150 ? fmtflags::scientific : fmtflags::fixed; 151 } 152 153 /////////////////////////////////////////////////////////////////////// 154 // Return the maximum number of decimal digits to generate in the 155 // fractional part of the output. 156 // 157 // n The floating point number to output. This can be used to 158 // adjust the required precision depending on the value of 159 // this number. If the trailing zeros flag is specified the 160 // fractional part of the output will be 'filled' with 161 // zeros, if appropriate 162 // 163 // Note: If the trailing_zeros flag is not in effect additional 164 // comments apply. See the comment for the fraction_part() 165 // function below. Moreover, this precision will be limited 166 // to the value of std::numeric_limits<T>::digits10 + 1 167 /////////////////////////////////////////////////////////////////////// 168 static unsigned precision(T) 169 { 170 // by default, generate max. 3 fractional digits 171 return 3; 172 } 173 174 /////////////////////////////////////////////////////////////////////// 175 // Generate the integer part of the number. 176 // 177 // sink The output iterator to use for generation 178 // n The absolute value of the integer part of the floating 179 // point number to convert (always non-negative). 180 // sign The sign of the overall floating point number to 181 // convert. 182 // force_sign Whether a sign has to be generated even for 183 // non-negative numbers 184 /////////////////////////////////////////////////////////////////////// 185 template <typename OutputIterator> 186 static bool integer_part (OutputIterator& sink, T n, bool sign 187 , bool force_sign) 188 { 189 return sign_inserter::call( 190 sink, traits::test_zero(n), sign, force_sign) && 191 int_inserter<10>::call(sink, n); 192 } 193 194 /////////////////////////////////////////////////////////////////////// 195 // Generate the decimal point. 196 // 197 // sink The output iterator to use for generation 198 // n The fractional part of the floating point number to 199 // convert. Note that this number is scaled such, that 200 // it represents the number of units which correspond 201 // to the value returned from the precision() function 202 // earlier. I.e. a fractional part of 0.01234 is 203 // represented as 1234 when the 'Precision' is 5. 204 // precision The number of digits to emit as returned by the 205 // function 'precision()' above 206 // 207 // This is given to allow to decide, whether a decimal point 208 // has to be generated at all. 209 // 210 // Note: If the trailing_zeros flag is not in effect additional 211 // comments apply. See the comment for the fraction_part() 212 // function below. 213 /////////////////////////////////////////////////////////////////////// 214 template <typename OutputIterator> 215 static bool dot (OutputIterator& sink, T /*n*/, unsigned /*precision*/) 216 { 217 return char_inserter<>::call(sink, '.'); // generate the dot by default 218 } 219 220 /////////////////////////////////////////////////////////////////////// 221 // Generate the fractional part of the number. 222 // 223 // sink The output iterator to use for generation 224 // n The fractional part of the floating point number to 225 // convert. This number is scaled such, that it represents 226 // the number of units which correspond to the 'Precision'. 227 // I.e. a fractional part of 0.01234 is represented as 1234 228 // when the 'precision_' parameter is 5. 229 // precision_ The corrected number of digits to emit (see note 230 // below) 231 // precision The number of digits to emit as returned by the 232 // function 'precision()' above 233 // 234 // Note: If trailing_zeros() does not return true the 'precision_' 235 // parameter will have been corrected from the value the 236 // precision() function returned earlier (defining the maximal 237 // number of fractional digits) in the sense, that it takes into 238 // account trailing zeros. I.e. a floating point number 0.0123 239 // and a value of 5 returned from precision() will result in: 240 // 241 // trailing_zeros is not specified: 242 // n 123 243 // precision_ 4 244 // 245 // trailing_zeros is specified: 246 // n 1230 247 // precision_ 5 248 // 249 /////////////////////////////////////////////////////////////////////// 250 template <typename OutputIterator> 251 static bool fraction_part (OutputIterator& sink, T n 252 , unsigned precision_, unsigned precision) 253 { 254 // allow for ADL to find the correct overload for floor and log10 255 using namespace std; 256 257 // The following is equivalent to: 258 // generate(sink, right_align(precision, '0')[ulong], n); 259 // but it's spelled out to avoid inter-modular dependencies. 260 261 typename remove_const<T>::type digits = 262 (traits::test_zero(n) ? 0 : floor(log10(n))) + 1; 263 bool r = true; 264 for (/**/; r && digits < precision_; digits = digits + 1) 265 r = char_inserter<>::call(sink, '0'); 266 if (precision && r) 267 r = int_inserter<10>::call(sink, n); 268 return r; 269 } 270 271 /////////////////////////////////////////////////////////////////////// 272 // Generate the exponential part of the number (this is called only 273 // if the floatfield() function returned the 'scientific' flag). 274 // 275 // sink The output iterator to use for generation 276 // n The (signed) exponential part of the floating point 277 // number to convert. 278 // 279 // The Tag template parameter is either of the type unused_type or 280 // describes the character class and conversion to be applied to any 281 // output possibly influenced by either the lower[...] or upper[...] 282 // directives. 283 /////////////////////////////////////////////////////////////////////// 284 template <typename CharEncoding, typename Tag, typename OutputIterator> 285 static bool exponent (OutputIterator& sink, long n) 286 { 287 long abs_n = traits::get_absolute_value(n); 288 bool r = char_inserter<CharEncoding, Tag>::call(sink, 'e') && 289 sign_inserter::call(sink, traits::test_zero(n) 290 , traits::test_negative(n), false); 291 292 // the C99 Standard requires at least two digits in the exponent 293 if (r && abs_n < 10) 294 r = char_inserter<CharEncoding, Tag>::call(sink, '0'); 295 return r && int_inserter<10>::call(sink, abs_n); 296 } 297 298 /////////////////////////////////////////////////////////////////////// 299 // Print the textual representations for non-normal floats (NaN and 300 // Inf) 301 // 302 // sink The output iterator to use for generation 303 // n The (signed) floating point number to convert. 304 // force_sign Whether a sign has to be generated even for 305 // non-negative numbers 306 // 307 // The Tag template parameter is either of the type unused_type or 308 // describes the character class and conversion to be applied to any 309 // output possibly influenced by either the lower[...] or upper[...] 310 // directives. 311 // 312 // Note: These functions get called only if fpclassify() returned 313 // FP_INFINITY or FP_NAN. 314 /////////////////////////////////////////////////////////////////////// 315 template <typename CharEncoding, typename Tag, typename OutputIterator> 316 static bool nan (OutputIterator& sink, T n, bool force_sign) 317 { 318 return sign_inserter::call( 319 sink, false, traits::test_negative(n), force_sign) && 320 string_inserter<CharEncoding, Tag>::call(sink, "nan"); 321 } 322 323 template <typename CharEncoding, typename Tag, typename OutputIterator> 324 static bool inf (OutputIterator& sink, T n, bool force_sign) 325 { 326 return sign_inserter::call( 327 sink, false, traits::test_negative(n), force_sign) && 328 string_inserter<CharEncoding, Tag>::call(sink, "inf"); 329 } 330 }; 331}}} 332 333#endif // defined(BOOST_SPIRIT_KARMA_REAL_POLICIES_MAR_02_2007_0936AM)