[857] | 1 | // Copyright (C) 2000 Stephen Cleary
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| 2 | //
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| 3 | // Distributed under the Boost Software License, Version 1.0. (See
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| 4 | // accompanying file LICENSE_1_0.txt or copy at
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| 5 | // http://www.boost.org/LICENSE_1_0.txt)
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| 6 | //
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| 7 | // See http://www.boost.org for updates, documentation, and revision history.
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| 8 |
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| 9 | #ifndef BOOST_POOL_CT_GCD_LCM_HPP
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| 10 | #define BOOST_POOL_CT_GCD_LCM_HPP
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| 11 |
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| 12 | #include <boost/static_assert.hpp>
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| 13 | #include <boost/type_traits/ice.hpp>
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| 14 |
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| 15 | namespace boost {
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| 16 |
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| 17 | namespace details {
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| 18 | namespace pool {
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| 19 |
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| 20 | // Compile-time calculation of greatest common divisor and least common multiple
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| 21 |
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| 22 | //
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| 23 | // ct_gcd is a compile-time algorithm that calculates the greatest common
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| 24 | // divisor of two unsigned integers, using Euclid's algorithm.
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| 25 | //
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| 26 | // assumes: A != 0 && B != 0
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| 27 | //
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| 28 |
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| 29 | #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
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| 30 |
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| 31 | namespace details {
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| 32 | template <unsigned A, unsigned B, bool Bis0>
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| 33 | struct ct_gcd_helper;
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| 34 | template <unsigned A, unsigned B>
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| 35 | struct ct_gcd_helper<A, B, false>
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| 36 | {
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| 37 | BOOST_STATIC_CONSTANT(unsigned, A_mod_B_ = A % B);
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| 38 | BOOST_STATIC_CONSTANT(unsigned, value =
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| 39 | (::boost::details::pool::details::ct_gcd_helper<
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| 40 | B, static_cast<unsigned>(A_mod_B_),
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| 41 | ::boost::type_traits::ice_eq<A_mod_B_, 0>::value
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| 42 | >::value) );
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| 43 | };
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| 44 | template <unsigned A, unsigned B>
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| 45 | struct ct_gcd_helper<A, B, true>
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| 46 | {
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| 47 | BOOST_STATIC_CONSTANT(unsigned, value = A);
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| 48 | };
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| 49 | } // namespace details
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| 50 |
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| 51 | template <unsigned A, unsigned B>
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| 52 | struct ct_gcd
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| 53 | {
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| 54 | BOOST_STATIC_ASSERT(A != 0 && B != 0);
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| 55 | BOOST_STATIC_CONSTANT(unsigned, value =
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| 56 | (::boost::details::pool::details::ct_gcd_helper<A, B, false>::value) );
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| 57 | };
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| 58 |
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| 59 | #else
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| 60 |
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| 61 | // Thanks to Peter Dimov for providing this workaround!
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| 62 | namespace details {
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| 63 | template<unsigned A> struct ct_gcd2
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| 64 | {
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| 65 | template<unsigned B>
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| 66 | struct helper
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| 67 | {
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| 68 | BOOST_STATIC_CONSTANT(unsigned, value = ct_gcd2<B>::helper<A % B>::value);
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| 69 | };
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| 70 | template<>
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| 71 | struct helper<0>
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| 72 | {
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| 73 | BOOST_STATIC_CONSTANT(unsigned, value = A);
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| 74 | };
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| 75 | };
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| 76 | } // namespace details
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| 77 |
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| 78 | template<unsigned A, unsigned B> struct ct_gcd
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| 79 | {
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| 80 | BOOST_STATIC_ASSERT(A != 0 && B != 0);
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| 81 | enum { value = details::ct_gcd2<A>::helper<B>::value };
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| 82 | };
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| 83 |
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| 84 | #endif
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| 85 |
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| 86 | //
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| 87 | // ct_lcm is a compile-time algorithm that calculates the least common
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| 88 | // multiple of two unsigned integers.
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| 89 | //
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| 90 | // assumes: A != 0 && B != 0
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| 91 | //
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| 92 | template <unsigned A, unsigned B>
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| 93 | struct ct_lcm
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| 94 | {
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| 95 | BOOST_STATIC_CONSTANT(unsigned, value =
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| 96 | (A / ::boost::details::pool::ct_gcd<A, B>::value * B) );
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| 97 | };
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| 98 |
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| 99 | } // namespace pool
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| 100 | } // namespace details
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| 101 |
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| 102 | } // namespace boost
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| 103 |
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| 104 | #endif
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