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include/boost/integer/common_factor_rt.hpp  view on Meta::CPAN

    {
       T temp = boost::integer::gcd_detail::optimal_gcd_select(a, b);
#if BOOST_WORKAROUND(BOOST_GCC_VERSION, < 40500)
       return (temp != T(0)) ? T(a / temp * b) : T(0);
#else
       return temp != T(0) ? T(a / temp * b) : T(0);
#endif
    }

} // namespace detail


template <typename Integer>
inline BOOST_CXX14_CONSTEXPR Integer gcd(Integer const &a, Integer const &b) BOOST_GCD_NOEXCEPT(Integer)
{
    if(a == (std::numeric_limits<Integer>::min)())
       return a == static_cast<Integer>(0) ? gcd_detail::gcd_traits<Integer>::abs(b) : boost::integer::gcd(static_cast<Integer>(a % b), b);
    else if (b == (std::numeric_limits<Integer>::min)())
       return b == static_cast<Integer>(0) ? gcd_detail::gcd_traits<Integer>::abs(a) : boost::integer::gcd(a, static_cast<Integer>(b % a));
    return gcd_detail::optimal_gcd_select(static_cast<Integer>(gcd_detail::gcd_traits<Integer>::abs(a)), static_cast<Integer>(gcd_detail::gcd_traits<Integer>::abs(b)));
}

template <typename Integer>
inline BOOST_CXX14_CONSTEXPR Integer lcm(Integer const &a, Integer const &b) BOOST_GCD_NOEXCEPT(Integer)
{
   return gcd_detail::lcm_imp(static_cast<Integer>(gcd_detail::gcd_traits<Integer>::abs(a)), static_cast<Integer>(gcd_detail::gcd_traits<Integer>::abs(b)));
}
#ifndef BOOST_NO_CXX11_VARIADIC_TEMPLATES
//
// This looks slightly odd, but the variadic forms must have 3 or more arguments, and the variadic argument pack may be empty.
// This matters not at all for most compilers, but Oracle C++ selects the wrong overload in the 2-arg case unless we do this.
//
template <typename Integer, typename... Args>
inline BOOST_CXX14_CONSTEXPR Integer gcd(Integer const &a, Integer const &b, const Integer& c, Args const&... args) BOOST_GCD_NOEXCEPT(Integer)
{
   Integer t = gcd(b, c, args...);
   return t == 1 ? 1 : gcd(a, t);
}

template <typename Integer, typename... Args>
inline BOOST_CXX14_CONSTEXPR Integer lcm(Integer const &a, Integer const &b, Integer const& c, Args const&... args) BOOST_GCD_NOEXCEPT(Integer)
{
   return lcm(a, lcm(b, c, args...));
}
#endif
//
// Special handling for rationals:
//
template <typename Integer>
inline typename boost::enable_if_c<std::numeric_limits<Integer>::is_specialized, boost::rational<Integer> >::type gcd(boost::rational<Integer> const &a, boost::rational<Integer> const &b)
{
   return boost::rational<Integer>(static_cast<Integer>(gcd(a.numerator(), b.numerator())), static_cast<Integer>(lcm(a.denominator(), b.denominator())));
}

template <typename Integer>
inline typename boost::enable_if_c<std::numeric_limits<Integer>::is_specialized, boost::rational<Integer> >::type lcm(boost::rational<Integer> const &a, boost::rational<Integer> const &b)
{
   return boost::rational<Integer>(static_cast<Integer>(lcm(a.numerator(), b.numerator())), static_cast<Integer>(gcd(a.denominator(), b.denominator())));
}
/**
 * Knuth, The Art of Computer Programming: Volume 2, Third edition, 1998
 * Chapter 4.5.2, Algorithm C: Greatest common divisor of n integers.
 *
 * Knuth counts down from n to zero but we naturally go from first to last.
 * We also return the termination position because it might be useful to know.
 * 
 * Partly by quirk, partly by design, this algorithm is defined for n = 1, 
 * because the gcd of {x} is x. It is not defined for n = 0.
 * 
 * @tparam  I   Input iterator.
 * @return  The gcd of the range and the iterator position at termination.
 */
template <typename I>
std::pair<typename std::iterator_traits<I>::value_type, I>
gcd_range(I first, I last) BOOST_GCD_NOEXCEPT(I)
{
    BOOST_ASSERT(first != last);
    typedef typename std::iterator_traits<I>::value_type T;
    
    T d = *first++;
    while (d != T(1) && first != last)
    {
        d = gcd(d, *first);
        first++;
    }
    return std::make_pair(d, first);
}
template <typename I>
std::pair<typename std::iterator_traits<I>::value_type, I>
lcm_range(I first, I last) BOOST_GCD_NOEXCEPT(I)
{
    BOOST_ASSERT(first != last);
    typedef typename std::iterator_traits<I>::value_type T;
    
    T d = *first++;
    while (d != T(1) && first != last)
    {
        d = lcm(d, *first);
        first++;
    }
    return std::make_pair(d, first);
}

template < typename IntegerType >
class gcd_evaluator
#ifdef BOOST_NO_CXX11_HDR_FUNCTIONAL
   : public std::binary_function<IntegerType, IntegerType, IntegerType>
#endif
{
public:
#ifndef BOOST_NO_CXX11_HDR_FUNCTIONAL
   typedef IntegerType first_argument_type;
   typedef IntegerType second_argument_type;
   typedef IntegerType result_type;
#endif
   IntegerType operator()(IntegerType const &a, IntegerType const &b)const
   {
      return boost::integer::gcd(a, b);
   }
};