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ratio revision 1.1.1.13
      1 // ratio -*- C++ -*-
      2 
      3 // Copyright (C) 2008-2022 Free Software Foundation, Inc.
      4 //
      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)
      9 // any later version.
     10 
     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.
     15 
     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.
     19 
     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/>.
     24 
     25 /** @file include/ratio
     26  *  This is a Standard C++ Library header.
     27  *  @ingroup ratio
     28  */
     29 
     30 #ifndef _GLIBCXX_RATIO
     31 #define _GLIBCXX_RATIO 1
     32 
     33 #pragma GCC system_header
     34 
     35 #if __cplusplus < 201103L
     36 # include <bits/c++0x_warning.h>
     37 #else
     38 
     39 #include <type_traits>
     40 #include <cstdint>		// intmax_t, uintmax_t
     41 
     42 namespace std _GLIBCXX_VISIBILITY(default)
     43 {
     44 _GLIBCXX_BEGIN_NAMESPACE_VERSION
     45 
     46   /**
     47    * @defgroup ratio Rational Arithmetic
     48    * @ingroup utilities
     49    *
     50    * Compile time representation of finite rational numbers.
     51    * @{
     52    */
     53 
     54   /// @cond undocumented
     55 
     56   template<intmax_t _Pn>
     57     struct __static_sign
     58     : integral_constant<intmax_t, (_Pn < 0) ? -1 : 1>
     59     { };
     60 
     61   template<intmax_t _Pn>
     62     struct __static_abs
     63     : integral_constant<intmax_t, _Pn * __static_sign<_Pn>::value>
     64     { };
     65 
     66   template<intmax_t _Pn, intmax_t _Qn>
     67     struct __static_gcd
     68     : __static_gcd<_Qn, (_Pn % _Qn)>
     69     { };
     70 
     71   template<intmax_t _Pn>
     72     struct __static_gcd<_Pn, 0>
     73     : integral_constant<intmax_t, __static_abs<_Pn>::value>
     74     { };
     75 
     76   template<intmax_t _Qn>
     77     struct __static_gcd<0, _Qn>
     78     : integral_constant<intmax_t, __static_abs<_Qn>::value>
     79     { };
     80 
     81   // Let c = 2^(half # of bits in an intmax_t)
     82   // then we find a1, a0, b1, b0 s.t. N = a1*c + a0, M = b1*c + b0
     83   // The multiplication of N and M becomes,
     84   // N * M = (a1 * b1)c^2 + (a0 * b1 + b0 * a1)c + a0 * b0
     85   // Multiplication is safe if each term and the sum of the terms
     86   // is representable by intmax_t.
     87   template<intmax_t _Pn, intmax_t _Qn>
     88     struct __safe_multiply
     89     {
     90     private:
     91       static const uintmax_t __c = uintmax_t(1) << (sizeof(intmax_t) * 4);
     92 
     93       static const uintmax_t __a0 = __static_abs<_Pn>::value % __c;
     94       static const uintmax_t __a1 = __static_abs<_Pn>::value / __c;
     95       static const uintmax_t __b0 = __static_abs<_Qn>::value % __c;
     96       static const uintmax_t __b1 = __static_abs<_Qn>::value / __c;
     97 
     98       static_assert(__a1 == 0 || __b1 == 0,
     99 		    "overflow in multiplication");
    100       static_assert(__a0 * __b1 + __b0 * __a1 < (__c >> 1),
    101 		    "overflow in multiplication");
    102       static_assert(__b0 * __a0 <= __INTMAX_MAX__,
    103 		    "overflow in multiplication");
    104       static_assert((__a0 * __b1 + __b0 * __a1) * __c
    105 		    <= __INTMAX_MAX__ -  __b0 * __a0,
    106 		    "overflow in multiplication");
    107 
    108     public:
    109       static const intmax_t value = _Pn * _Qn;
    110     };
    111 
    112   // Some double-precision utilities, where numbers are represented as
    113   // __hi*2^(8*sizeof(uintmax_t)) + __lo.
    114   template<uintmax_t __hi1, uintmax_t __lo1, uintmax_t __hi2, uintmax_t __lo2>
    115     struct __big_less
    116     : integral_constant<bool, (__hi1 < __hi2
    117 			       || (__hi1 == __hi2 && __lo1 < __lo2))>
    118     { };
    119 
    120   template<uintmax_t __hi1, uintmax_t __lo1, uintmax_t __hi2, uintmax_t __lo2>
    121     struct __big_add
    122     {
    123       static constexpr uintmax_t __lo = __lo1 + __lo2;
    124       static constexpr uintmax_t __hi = (__hi1 + __hi2 +
    125 					 (__lo1 + __lo2 < __lo1)); // carry
    126     };
    127 
    128   // Subtract a number from a bigger one.
    129   template<uintmax_t __hi1, uintmax_t __lo1, uintmax_t __hi2, uintmax_t __lo2>
    130     struct __big_sub
    131     {
    132       static_assert(!__big_less<__hi1, __lo1, __hi2, __lo2>::value,
    133 		    "Internal library error");
    134       static constexpr uintmax_t __lo = __lo1 - __lo2;
    135       static constexpr uintmax_t __hi = (__hi1 - __hi2 -
    136 					 (__lo1 < __lo2)); // carry
    137     };
    138 
    139   // Same principle as __safe_multiply.
    140   template<uintmax_t __x, uintmax_t __y>
    141     struct __big_mul
    142     {
    143     private:
    144       static constexpr uintmax_t __c = uintmax_t(1) << (sizeof(intmax_t) * 4);
    145       static constexpr uintmax_t __x0 = __x % __c;
    146       static constexpr uintmax_t __x1 = __x / __c;
    147       static constexpr uintmax_t __y0 = __y % __c;
    148       static constexpr uintmax_t __y1 = __y / __c;
    149       static constexpr uintmax_t __x0y0 = __x0 * __y0;
    150       static constexpr uintmax_t __x0y1 = __x0 * __y1;
    151       static constexpr uintmax_t __x1y0 = __x1 * __y0;
    152       static constexpr uintmax_t __x1y1 = __x1 * __y1;
    153       static constexpr uintmax_t __mix = __x0y1 + __x1y0; // possible carry...
    154       static constexpr uintmax_t __mix_lo = __mix * __c;
    155       static constexpr uintmax_t __mix_hi
    156       = __mix / __c + ((__mix < __x0y1) ? __c : 0); // ... added here
    157       typedef __big_add<__mix_hi, __mix_lo, __x1y1, __x0y0> _Res;
    158     public:
    159       static constexpr uintmax_t __hi = _Res::__hi;
    160       static constexpr uintmax_t __lo = _Res::__lo;
    161     };
    162 
    163   // Adapted from __udiv_qrnnd_c in longlong.h
    164   // This version assumes that the high bit of __d is 1.
    165   template<uintmax_t __n1, uintmax_t __n0, uintmax_t __d>
    166     struct __big_div_impl
    167     {
    168     private:
    169       static_assert(__d >= (uintmax_t(1) << (sizeof(intmax_t) * 8 - 1)),
    170 		    "Internal library error");
    171       static_assert(__n1 < __d, "Internal library error");
    172       static constexpr uintmax_t __c = uintmax_t(1) << (sizeof(intmax_t) * 4);
    173       static constexpr uintmax_t __d1 = __d / __c;
    174       static constexpr uintmax_t __d0 = __d % __c;
    175 
    176       static constexpr uintmax_t __q1x = __n1 / __d1;
    177       static constexpr uintmax_t __r1x = __n1 % __d1;
    178       static constexpr uintmax_t __m = __q1x * __d0;
    179       static constexpr uintmax_t __r1y = __r1x * __c + __n0 / __c;
    180       static constexpr uintmax_t __r1z = __r1y + __d;
    181       static constexpr uintmax_t __r1
    182       = ((__r1y < __m) ? ((__r1z >= __d) && (__r1z < __m))
    183 	 ? (__r1z + __d) : __r1z : __r1y) - __m;
    184       static constexpr uintmax_t __q1
    185       = __q1x - ((__r1y < __m)
    186 		 ? ((__r1z >= __d) && (__r1z < __m)) ? 2 : 1 : 0);
    187       static constexpr uintmax_t __q0x = __r1 / __d1;
    188       static constexpr uintmax_t __r0x = __r1 % __d1;
    189       static constexpr uintmax_t __n = __q0x * __d0;
    190       static constexpr uintmax_t __r0y = __r0x * __c + __n0 % __c;
    191       static constexpr uintmax_t __r0z = __r0y + __d;
    192       static constexpr uintmax_t __r0
    193       = ((__r0y < __n) ? ((__r0z >= __d) && (__r0z < __n))
    194 	 ? (__r0z + __d) : __r0z : __r0y) - __n;
    195       static constexpr uintmax_t __q0
    196       = __q0x - ((__r0y < __n) ? ((__r0z >= __d)
    197 				  && (__r0z < __n)) ? 2 : 1 : 0);
    198 
    199     public:
    200       static constexpr uintmax_t __quot = __q1 * __c + __q0;
    201       static constexpr uintmax_t __rem = __r0;
    202 
    203     private:
    204       typedef __big_mul<__quot, __d> _Prod;
    205       typedef __big_add<_Prod::__hi, _Prod::__lo, 0, __rem> _Sum;
    206       static_assert(_Sum::__hi == __n1 && _Sum::__lo == __n0,
    207 		    "Internal library error");
    208   };
    209 
    210   template<uintmax_t __n1, uintmax_t __n0, uintmax_t __d>
    211     struct __big_div
    212     {
    213     private:
    214       static_assert(__d != 0, "Internal library error");
    215       static_assert(sizeof (uintmax_t) == sizeof (unsigned long long),
    216 		    "This library calls __builtin_clzll on uintmax_t, which "
    217 		    "is unsafe on your platform. Please complain to "
    218 		    "http://gcc.gnu.org/bugzilla/");
    219       static constexpr int __shift = __builtin_clzll(__d);
    220       static constexpr int __coshift_ = sizeof(uintmax_t) * 8 - __shift;
    221       static constexpr int __coshift = (__shift != 0) ? __coshift_ : 0;
    222       static constexpr uintmax_t __c1 = uintmax_t(1) << __shift;
    223       static constexpr uintmax_t __c2 = uintmax_t(1) << __coshift;
    224       static constexpr uintmax_t __new_d = __d * __c1;
    225       static constexpr uintmax_t __new_n0 = __n0 * __c1;
    226       static constexpr uintmax_t __n1_shifted = (__n1 % __d) * __c1;
    227       static constexpr uintmax_t __n0_top = (__shift != 0) ? (__n0 / __c2) : 0;
    228       static constexpr uintmax_t __new_n1 = __n1_shifted + __n0_top;
    229       typedef __big_div_impl<__new_n1, __new_n0, __new_d> _Res;
    230 
    231     public:
    232       static constexpr uintmax_t __quot_hi = __n1 / __d;
    233       static constexpr uintmax_t __quot_lo = _Res::__quot;
    234       static constexpr uintmax_t __rem = _Res::__rem / __c1;
    235 
    236     private:
    237       typedef __big_mul<__quot_lo, __d> _P0;
    238       typedef __big_mul<__quot_hi, __d> _P1;
    239       typedef __big_add<_P0::__hi, _P0::__lo, _P1::__lo, __rem> _Sum;
    240       // No overflow.
    241       static_assert(_P1::__hi == 0, "Internal library error");
    242       static_assert(_Sum::__hi >= _P0::__hi, "Internal library error");
    243       // Matches the input data.
    244       static_assert(_Sum::__hi == __n1 && _Sum::__lo == __n0,
    245 		    "Internal library error");
    246       static_assert(__rem < __d, "Internal library error");
    247     };
    248 
    249   /// @endcond
    250 
    251   /**
    252    *  @brief Provides compile-time rational arithmetic.
    253    *
    254    *  This class template represents any finite rational number with a
    255    *  numerator and denominator representable by compile-time constants of
    256    *  type intmax_t. The ratio is simplified when instantiated.
    257    *
    258    *  For example:
    259    *  @code
    260    *    std::ratio<7,-21>::num == -1;
    261    *    std::ratio<7,-21>::den == 3;
    262    *  @endcode
    263    *
    264   */
    265   template<intmax_t _Num, intmax_t _Den = 1>
    266     struct ratio
    267     {
    268       static_assert(_Den != 0, "denominator cannot be zero");
    269       static_assert(_Num >= -__INTMAX_MAX__ && _Den >= -__INTMAX_MAX__,
    270 		    "out of range");
    271 
    272       // Note: sign(N) * abs(N) == N
    273       static constexpr intmax_t num =
    274         _Num * __static_sign<_Den>::value / __static_gcd<_Num, _Den>::value;
    275 
    276       static constexpr intmax_t den =
    277         __static_abs<_Den>::value / __static_gcd<_Num, _Den>::value;
    278 
    279       typedef ratio<num, den> type;
    280     };
    281 
    282 #if ! __cpp_inline_variables
    283   template<intmax_t _Num, intmax_t _Den>
    284     constexpr intmax_t ratio<_Num, _Den>::num;
    285 
    286   template<intmax_t _Num, intmax_t _Den>
    287     constexpr intmax_t ratio<_Num, _Den>::den;
    288 #endif
    289 
    290   /// @cond undocumented
    291 
    292   template<typename _Tp>
    293     struct __is_ratio
    294     : std::false_type
    295     { };
    296 
    297   template<intmax_t _Num, intmax_t _Den>
    298     struct __is_ratio<ratio<_Num, _Den>>
    299     : std::true_type
    300     { };
    301 
    302 #if __cpp_variable_templates
    303   template<typename _Tp>
    304     constexpr bool __is_ratio_v = false;
    305   template<intmax_t _Num, intmax_t _Den>
    306     constexpr bool __is_ratio_v<ratio<_Num, _Den>> = true;
    307 #endif
    308 
    309   template<typename _R1, typename _R2>
    310     constexpr bool
    311     __are_both_ratios() noexcept
    312     {
    313 #if __cpp_variable_templates && __cpp_if_constexpr
    314       if constexpr (__is_ratio_v<_R1>)
    315 	if constexpr (__is_ratio_v<_R2>)
    316 	  return true;
    317       return false;
    318 #else
    319       return __and_<__is_ratio<_R1>, __is_ratio<_R2>>::value;
    320 #endif
    321     }
    322 
    323   template<typename _R1, typename _R2>
    324     struct __ratio_multiply
    325     {
    326       static_assert(std::__are_both_ratios<_R1, _R2>(),
    327 		    "both template arguments must be a std::ratio");
    328 
    329     private:
    330       static const intmax_t __gcd1 =
    331         __static_gcd<_R1::num, _R2::den>::value;
    332       static const intmax_t __gcd2 =
    333         __static_gcd<_R2::num, _R1::den>::value;
    334 
    335     public:
    336       typedef ratio<
    337         __safe_multiply<(_R1::num / __gcd1),
    338                         (_R2::num / __gcd2)>::value,
    339         __safe_multiply<(_R1::den / __gcd2),
    340                         (_R2::den / __gcd1)>::value> type;
    341 
    342       static constexpr intmax_t num = type::num;
    343       static constexpr intmax_t den = type::den;
    344     };
    345 
    346 #if ! __cpp_inline_variables
    347   template<typename _R1, typename _R2>
    348     constexpr intmax_t __ratio_multiply<_R1, _R2>::num;
    349 
    350   template<typename _R1, typename _R2>
    351     constexpr intmax_t __ratio_multiply<_R1, _R2>::den;
    352 #endif
    353 
    354   /// @endcond
    355 
    356   /// ratio_multiply
    357   template<typename _R1, typename _R2>
    358     using ratio_multiply = typename __ratio_multiply<_R1, _R2>::type;
    359 
    360   /// @cond undocumented
    361 
    362   template<typename _R1, typename _R2>
    363     struct __ratio_divide
    364     {
    365       static_assert(_R2::num != 0, "division by 0");
    366 
    367       typedef typename __ratio_multiply<
    368         _R1,
    369         ratio<_R2::den, _R2::num>>::type type;
    370 
    371       static constexpr intmax_t num = type::num;
    372       static constexpr intmax_t den = type::den;
    373     };
    374 
    375 #if ! __cpp_inline_variables
    376   template<typename _R1, typename _R2>
    377     constexpr intmax_t __ratio_divide<_R1, _R2>::num;
    378 
    379   template<typename _R1, typename _R2>
    380     constexpr intmax_t __ratio_divide<_R1, _R2>::den;
    381 #endif
    382 
    383   /// @endcond
    384 
    385   /// ratio_divide
    386   template<typename _R1, typename _R2>
    387     using ratio_divide = typename __ratio_divide<_R1, _R2>::type;
    388 
    389   /// ratio_equal
    390   template<typename _R1, typename _R2>
    391     struct ratio_equal
    392     : integral_constant<bool, _R1::num == _R2::num && _R1::den == _R2::den>
    393     {
    394       static_assert(std::__are_both_ratios<_R1, _R2>(),
    395 		    "both template arguments must be a std::ratio");
    396     };
    397 
    398   /// ratio_not_equal
    399   template<typename _R1, typename _R2>
    400     struct ratio_not_equal
    401     : integral_constant<bool, !ratio_equal<_R1, _R2>::value>
    402     { };
    403 
    404   /// @cond undocumented
    405 
    406   // Both numbers are positive.
    407   template<typename _R1, typename _R2,
    408            typename _Left = __big_mul<_R1::num,_R2::den>,
    409            typename _Right = __big_mul<_R2::num,_R1::den> >
    410     struct __ratio_less_impl_1
    411     : integral_constant<bool, __big_less<_Left::__hi, _Left::__lo,
    412            _Right::__hi, _Right::__lo>::value>
    413     { };
    414 
    415   template<typename _R1, typename _R2,
    416 	   bool = (_R1::num == 0 || _R2::num == 0
    417 		   || (__static_sign<_R1::num>::value
    418 		       != __static_sign<_R2::num>::value)),
    419 	   bool = (__static_sign<_R1::num>::value == -1
    420 		   && __static_sign<_R2::num>::value == -1)>
    421     struct __ratio_less_impl
    422     : __ratio_less_impl_1<_R1, _R2>::type
    423     { };
    424 
    425   template<typename _R1, typename _R2>
    426     struct __ratio_less_impl<_R1, _R2, true, false>
    427     : integral_constant<bool, _R1::num < _R2::num>
    428     { };
    429 
    430   template<typename _R1, typename _R2>
    431     struct __ratio_less_impl<_R1, _R2, false, true>
    432     : __ratio_less_impl_1<ratio<-_R2::num, _R2::den>,
    433            ratio<-_R1::num, _R1::den> >::type
    434     { };
    435 
    436   /// @endcond
    437 
    438   /// ratio_less
    439   template<typename _R1, typename _R2>
    440     struct ratio_less
    441     : __ratio_less_impl<_R1, _R2>::type
    442     {
    443       static_assert(std::__are_both_ratios<_R1, _R2>(),
    444 		    "both template arguments must be a std::ratio");
    445     };
    446 
    447   /// ratio_less_equal
    448   template<typename _R1, typename _R2>
    449     struct ratio_less_equal
    450     : integral_constant<bool, !ratio_less<_R2, _R1>::value>
    451     { };
    452 
    453   /// ratio_greater
    454   template<typename _R1, typename _R2>
    455     struct ratio_greater
    456     : integral_constant<bool, ratio_less<_R2, _R1>::value>
    457     { };
    458 
    459   /// ratio_greater_equal
    460   template<typename _R1, typename _R2>
    461     struct ratio_greater_equal
    462     : integral_constant<bool, !ratio_less<_R1, _R2>::value>
    463     { };
    464 
    465 #if __cplusplus > 201402L
    466   template <typename _R1, typename _R2>
    467     inline constexpr bool ratio_equal_v = ratio_equal<_R1, _R2>::value;
    468   template <typename _R1, typename _R2>
    469     inline constexpr bool ratio_not_equal_v = ratio_not_equal<_R1, _R2>::value;
    470   template <typename _R1, typename _R2>
    471     inline constexpr bool ratio_less_v = ratio_less<_R1, _R2>::value;
    472   template <typename _R1, typename _R2>
    473     inline constexpr bool ratio_less_equal_v
    474       = ratio_less_equal<_R1, _R2>::value;
    475   template <typename _R1, typename _R2>
    476     inline constexpr bool ratio_greater_v = ratio_greater<_R1, _R2>::value;
    477   template <typename _R1, typename _R2>
    478     inline constexpr bool ratio_greater_equal_v
    479       = ratio_greater_equal<_R1, _R2>::value;
    480 #endif // C++17
    481 
    482   /// @cond undocumented
    483 
    484   template<typename _R1, typename _R2,
    485       bool = (_R1::num >= 0),
    486       bool = (_R2::num >= 0),
    487       bool = ratio_less<ratio<__static_abs<_R1::num>::value, _R1::den>,
    488         ratio<__static_abs<_R2::num>::value, _R2::den> >::value>
    489     struct __ratio_add_impl
    490     {
    491     private:
    492       typedef typename __ratio_add_impl<
    493         ratio<-_R1::num, _R1::den>,
    494         ratio<-_R2::num, _R2::den> >::type __t;
    495     public:
    496       typedef ratio<-__t::num, __t::den> type;
    497     };
    498 
    499   // True addition of nonnegative numbers.
    500   template<typename _R1, typename _R2, bool __b>
    501     struct __ratio_add_impl<_R1, _R2, true, true, __b>
    502     {
    503     private:
    504       static constexpr uintmax_t __g = __static_gcd<_R1::den, _R2::den>::value;
    505       static constexpr uintmax_t __d2 = _R2::den / __g;
    506       typedef __big_mul<_R1::den, __d2> __d;
    507       typedef __big_mul<_R1::num, _R2::den / __g> __x;
    508       typedef __big_mul<_R2::num, _R1::den / __g> __y;
    509       typedef __big_add<__x::__hi, __x::__lo, __y::__hi, __y::__lo> __n;
    510       static_assert(__n::__hi >= __x::__hi, "Internal library error");
    511       typedef __big_div<__n::__hi, __n::__lo, __g> __ng;
    512       static constexpr uintmax_t __g2 = __static_gcd<__ng::__rem, __g>::value;
    513       typedef __big_div<__n::__hi, __n::__lo, __g2> __n_final;
    514       static_assert(__n_final::__rem == 0, "Internal library error");
    515       static_assert(__n_final::__quot_hi == 0 &&
    516         __n_final::__quot_lo <= __INTMAX_MAX__, "overflow in addition");
    517       typedef __big_mul<_R1::den / __g2, __d2> __d_final;
    518       static_assert(__d_final::__hi == 0 &&
    519         __d_final::__lo <= __INTMAX_MAX__, "overflow in addition");
    520     public:
    521       typedef ratio<__n_final::__quot_lo, __d_final::__lo> type;
    522     };
    523 
    524   template<typename _R1, typename _R2>
    525     struct __ratio_add_impl<_R1, _R2, false, true, true>
    526     : __ratio_add_impl<_R2, _R1>
    527     { };
    528 
    529   // True subtraction of nonnegative numbers yielding a nonnegative result.
    530   template<typename _R1, typename _R2>
    531     struct __ratio_add_impl<_R1, _R2, true, false, false>
    532     {
    533     private:
    534       static constexpr uintmax_t __g = __static_gcd<_R1::den, _R2::den>::value;
    535       static constexpr uintmax_t __d2 = _R2::den / __g;
    536       typedef __big_mul<_R1::den, __d2> __d;
    537       typedef __big_mul<_R1::num, _R2::den / __g> __x;
    538       typedef __big_mul<-_R2::num, _R1::den / __g> __y;
    539       typedef __big_sub<__x::__hi, __x::__lo, __y::__hi, __y::__lo> __n;
    540       typedef __big_div<__n::__hi, __n::__lo, __g> __ng;
    541       static constexpr uintmax_t __g2 = __static_gcd<__ng::__rem, __g>::value;
    542       typedef __big_div<__n::__hi, __n::__lo, __g2> __n_final;
    543       static_assert(__n_final::__rem == 0, "Internal library error");
    544       static_assert(__n_final::__quot_hi == 0 &&
    545         __n_final::__quot_lo <= __INTMAX_MAX__, "overflow in addition");
    546       typedef __big_mul<_R1::den / __g2, __d2> __d_final;
    547       static_assert(__d_final::__hi == 0 &&
    548         __d_final::__lo <= __INTMAX_MAX__, "overflow in addition");
    549     public:
    550       typedef ratio<__n_final::__quot_lo, __d_final::__lo> type;
    551     };
    552 
    553   template<typename _R1, typename _R2>
    554     struct __ratio_add
    555     {
    556       static_assert(std::__are_both_ratios<_R1, _R2>(),
    557 		    "both template arguments must be a std::ratio");
    558 
    559       typedef typename __ratio_add_impl<_R1, _R2>::type type;
    560       static constexpr intmax_t num = type::num;
    561       static constexpr intmax_t den = type::den;
    562     };
    563 
    564 #if ! __cpp_inline_variables
    565   template<typename _R1, typename _R2>
    566     constexpr intmax_t __ratio_add<_R1, _R2>::num;
    567 
    568   template<typename _R1, typename _R2>
    569     constexpr intmax_t __ratio_add<_R1, _R2>::den;
    570 #endif
    571 
    572   /// @endcond
    573 
    574   /// ratio_add
    575   template<typename _R1, typename _R2>
    576     using ratio_add = typename __ratio_add<_R1, _R2>::type;
    577 
    578   /// @cond undocumented
    579 
    580   template<typename _R1, typename _R2>
    581     struct __ratio_subtract
    582     {
    583       typedef typename __ratio_add<
    584         _R1,
    585         ratio<-_R2::num, _R2::den>>::type type;
    586 
    587       static constexpr intmax_t num = type::num;
    588       static constexpr intmax_t den = type::den;
    589     };
    590 
    591 #if ! __cpp_inline_variables
    592   template<typename _R1, typename _R2>
    593     constexpr intmax_t __ratio_subtract<_R1, _R2>::num;
    594 
    595   template<typename _R1, typename _R2>
    596     constexpr intmax_t __ratio_subtract<_R1, _R2>::den;
    597 #endif
    598 
    599   /// @endcond
    600 
    601   /// ratio_subtract
    602   template<typename _R1, typename _R2>
    603     using ratio_subtract = typename __ratio_subtract<_R1, _R2>::type;
    604 
    605 
    606   typedef ratio<1,       1000000000000000000> atto;
    607   typedef ratio<1,          1000000000000000> femto;
    608   typedef ratio<1,             1000000000000> pico;
    609   typedef ratio<1,                1000000000> nano;
    610   typedef ratio<1,                   1000000> micro;
    611   typedef ratio<1,                      1000> milli;
    612   typedef ratio<1,                       100> centi;
    613   typedef ratio<1,                        10> deci;
    614   typedef ratio<                       10, 1> deca;
    615   typedef ratio<                      100, 1> hecto;
    616   typedef ratio<                     1000, 1> kilo;
    617   typedef ratio<                  1000000, 1> mega;
    618   typedef ratio<               1000000000, 1> giga;
    619   typedef ratio<            1000000000000, 1> tera;
    620   typedef ratio<         1000000000000000, 1> peta;
    621   typedef ratio<      1000000000000000000, 1> exa;
    622 
    623   /// @} group ratio
    624 _GLIBCXX_END_NAMESPACE_VERSION
    625 } // namespace
    626 
    627 #endif // C++11
    628 
    629 #endif //_GLIBCXX_RATIO
    630