3 // Copyright (C) 2008, 2009, 2010 Free Software Foundation, Inc.
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
25 /** @file include/ratio
26 * This is a Standard C++ Library header.
29 #ifndef _GLIBCXX_RATIO
30 #define _GLIBCXX_RATIO 1
32 #pragma GCC system_header
34 #ifndef __GXX_EXPERIMENTAL_CXX0X__
35 # include <bits/c++0x_warning.h>
38 #include <type_traits>
41 #ifdef _GLIBCXX_USE_C99_STDINT_TR1
43 namespace std _GLIBCXX_VISIBILITY(default)
45 _GLIBCXX_BEGIN_NAMESPACE_VERSION
48 * @defgroup ratio Rational Arithmetic
51 * Compile time representation of finite rational numbers.
55 template<intmax_t _Pn>
57 : integral_constant<intmax_t, (_Pn < 0) ? -1 : 1>
60 template<intmax_t _Pn>
62 : integral_constant<intmax_t, _Pn * __static_sign<_Pn>::value>
65 template<intmax_t _Pn, intmax_t _Qn>
68 template<intmax_t _Pn, intmax_t _Qn>
70 : __static_gcd<_Qn, (_Pn % _Qn)>
73 template<intmax_t _Pn>
74 struct __static_gcd<_Pn, 0>
75 : integral_constant<intmax_t, __static_abs<_Pn>::value>
78 template<intmax_t _Qn>
79 struct __static_gcd<0, _Qn>
80 : integral_constant<intmax_t, __static_abs<_Qn>::value>
83 // Let c = 2^(half # of bits in an intmax_t)
84 // then we find a1, a0, b1, b0 s.t. N = a1*c + a0, M = b1*c + b0
85 // The multiplication of N and M becomes,
86 // N * M = (a1 * b1)c^2 + (a0 * b1 + b0 * a1)c + a0 * b0
87 // Multiplication is safe if each term and the sum of the terms
88 // is representable by intmax_t.
89 template<intmax_t _Pn, intmax_t _Qn>
90 struct __safe_multiply
93 static const uintmax_t __c = uintmax_t(1) << (sizeof(intmax_t) * 4);
95 static const uintmax_t __a0 = __static_abs<_Pn>::value % __c;
96 static const uintmax_t __a1 = __static_abs<_Pn>::value / __c;
97 static const uintmax_t __b0 = __static_abs<_Qn>::value % __c;
98 static const uintmax_t __b1 = __static_abs<_Qn>::value / __c;
100 static_assert(__a1 == 0 || __b1 == 0,
101 "overflow in multiplication");
102 static_assert(__a0 * __b1 + __b0 * __a1 < (__c >> 1),
103 "overflow in multiplication");
104 static_assert(__b0 * __a0 <= __INTMAX_MAX__,
105 "overflow in multiplication");
106 static_assert((__a0 * __b1 + __b0 * __a1) * __c <=
107 __INTMAX_MAX__ - __b0 * __a0, "overflow in multiplication");
110 static const intmax_t value = _Pn * _Qn;
113 // Helpers for __safe_add
114 template<intmax_t _Pn, intmax_t _Qn, bool>
115 struct __add_overflow_check_impl
116 : integral_constant<bool, (_Pn <= __INTMAX_MAX__ - _Qn)>
119 template<intmax_t _Pn, intmax_t _Qn>
120 struct __add_overflow_check_impl<_Pn, _Qn, false>
121 : integral_constant<bool, (_Pn >= -__INTMAX_MAX__ - _Qn)>
124 template<intmax_t _Pn, intmax_t _Qn>
125 struct __add_overflow_check
126 : __add_overflow_check_impl<_Pn, _Qn, (_Qn >= 0)>
129 template<intmax_t _Pn, intmax_t _Qn>
132 static_assert(__add_overflow_check<_Pn, _Qn>::value != 0,
133 "overflow in addition");
135 static const intmax_t value = _Pn + _Qn;
139 * @brief Provides compile-time rational arithmetic.
141 * This class template represents any finite rational number with a
142 * numerator and denominator representable by compile-time constants of
143 * type intmax_t. The ratio is simplified when instantiated.
147 * std::ratio<7,-21>::num == -1;
148 * std::ratio<7,-21>::den == 3;
152 template<intmax_t _Num, intmax_t _Den = 1>
155 static_assert(_Den != 0, "denominator cannot be zero");
156 static_assert(_Num >= -__INTMAX_MAX__ && _Den >= -__INTMAX_MAX__,
159 // Note: sign(N) * abs(N) == N
160 static constexpr intmax_t num =
161 _Num * __static_sign<_Den>::value / __static_gcd<_Num, _Den>::value;
163 static constexpr intmax_t den =
164 __static_abs<_Den>::value / __static_gcd<_Num, _Den>::value;
166 typedef ratio<num, den> type;
169 template<intmax_t _Num, intmax_t _Den>
170 constexpr intmax_t ratio<_Num, _Den>::num;
172 template<intmax_t _Num, intmax_t _Den>
173 constexpr intmax_t ratio<_Num, _Den>::den;
176 template<typename _R1, typename _R2>
180 static const intmax_t __gcd =
181 __static_gcd<_R1::den, _R2::den>::value;
186 __safe_multiply<_R1::num, (_R2::den / __gcd)>::value,
187 __safe_multiply<_R2::num, (_R1::den / __gcd)>::value>::value,
188 __safe_multiply<_R1::den, (_R2::den / __gcd)>::value> type;
190 static constexpr intmax_t num = type::num;
191 static constexpr intmax_t den = type::den;
194 template<typename _R1, typename _R2>
195 constexpr intmax_t ratio_add<_R1, _R2>::num;
197 template<typename _R1, typename _R2>
198 constexpr intmax_t ratio_add<_R1, _R2>::den;
201 template<typename _R1, typename _R2>
202 struct ratio_subtract
204 typedef typename ratio_add<
206 ratio<-_R2::num, _R2::den>>::type type;
208 static constexpr intmax_t num = type::num;
209 static constexpr intmax_t den = type::den;
212 template<typename _R1, typename _R2>
213 constexpr intmax_t ratio_subtract<_R1, _R2>::num;
215 template<typename _R1, typename _R2>
216 constexpr intmax_t ratio_subtract<_R1, _R2>::den;
219 template<typename _R1, typename _R2>
220 struct ratio_multiply
223 static const intmax_t __gcd1 =
224 __static_gcd<_R1::num, _R2::den>::value;
225 static const intmax_t __gcd2 =
226 __static_gcd<_R2::num, _R1::den>::value;
230 __safe_multiply<(_R1::num / __gcd1),
231 (_R2::num / __gcd2)>::value,
232 __safe_multiply<(_R1::den / __gcd2),
233 (_R2::den / __gcd1)>::value> type;
235 static constexpr intmax_t num = type::num;
236 static constexpr intmax_t den = type::den;
239 template<typename _R1, typename _R2>
240 constexpr intmax_t ratio_multiply<_R1, _R2>::num;
242 template<typename _R1, typename _R2>
243 constexpr intmax_t ratio_multiply<_R1, _R2>::den;
246 template<typename _R1, typename _R2>
249 static_assert(_R2::num != 0, "division by 0");
251 typedef typename ratio_multiply<
253 ratio<_R2::den, _R2::num>>::type type;
255 static constexpr intmax_t num = type::num;
256 static constexpr intmax_t den = type::den;
259 template<typename _R1, typename _R2>
260 constexpr intmax_t ratio_divide<_R1, _R2>::num;
262 template<typename _R1, typename _R2>
263 constexpr intmax_t ratio_divide<_R1, _R2>::den;
266 template<typename _R1, typename _R2>
268 : integral_constant<bool, _R1::num == _R2::num && _R1::den == _R2::den>
272 template<typename _R1, typename _R2>
273 struct ratio_not_equal
274 : integral_constant<bool, !ratio_equal<_R1, _R2>::value>
277 template<typename _R1>
278 struct __ratio_less_impl_1
279 : integral_constant<bool, _R1::num < _R1::den>
282 template<typename _R1, typename _R2,
283 bool = (_R1::num == 0 || _R2::num == 0
284 || (__static_sign<_R1::num>::value
285 != __static_sign<_R2::num>::value)),
286 bool = (__static_sign<_R1::num>::value == -1
287 && __static_sign<_R2::num>::value == -1)>
288 struct __ratio_less_impl
289 : __ratio_less_impl_1<typename ratio_divide<_R1, _R2>::type>::type
292 template<typename _R1, typename _R2>
293 struct __ratio_less_impl<_R1, _R2, true, false>
294 : integral_constant<bool, _R1::num < _R2::num>
297 template<typename _R1, typename _R2>
298 struct __ratio_less_impl<_R1, _R2, false, true>
299 : __ratio_less_impl_1<typename ratio_divide<_R2, _R1>::type>::type
303 template<typename _R1, typename _R2>
305 : __ratio_less_impl<_R1, _R2>::type
309 template<typename _R1, typename _R2>
310 struct ratio_less_equal
311 : integral_constant<bool, !ratio_less<_R2, _R1>::value>
315 template<typename _R1, typename _R2>
317 : integral_constant<bool, ratio_less<_R2, _R1>::value>
320 /// ratio_greater_equal
321 template<typename _R1, typename _R2>
322 struct ratio_greater_equal
323 : integral_constant<bool, !ratio_less<_R1, _R2>::value>
326 typedef ratio<1, 1000000000000000000> atto;
327 typedef ratio<1, 1000000000000000> femto;
328 typedef ratio<1, 1000000000000> pico;
329 typedef ratio<1, 1000000000> nano;
330 typedef ratio<1, 1000000> micro;
331 typedef ratio<1, 1000> milli;
332 typedef ratio<1, 100> centi;
333 typedef ratio<1, 10> deci;
334 typedef ratio< 10, 1> deca;
335 typedef ratio< 100, 1> hecto;
336 typedef ratio< 1000, 1> kilo;
337 typedef ratio< 1000000, 1> mega;
338 typedef ratio< 1000000000, 1> giga;
339 typedef ratio< 1000000000000, 1> tera;
340 typedef ratio< 1000000000000000, 1> peta;
341 typedef ratio< 1000000000000000000, 1> exa;
344 _GLIBCXX_END_NAMESPACE_VERSION
347 #endif //_GLIBCXX_USE_C99_STDINT_TR1
349 #endif //__GXX_EXPERIMENTAL_CXX0X__
351 #endif //_GLIBCXX_RATIO