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#include <Functions/FunctionFactory.h>
#include <Functions/FunctionBinaryArithmetic.h>
#include <Functions/GCDLCMImpl.h>
#include <boost/integer/common_factor.hpp>
namespace
{
template <typename T>
constexpr T abs(T value) noexcept
{
if constexpr (std::is_signed_v<T>)
{
if (value >= 0 || value == std::numeric_limits<T>::min())
return value;
return -value;
}
else
return value;
}
}
namespace DB
{
namespace
{
struct NameLCM { static constexpr auto name = "lcm"; };
template <typename A, typename B>
struct LCMImpl : public GCDLCMImpl<A, B, LCMImpl<A, B>, NameLCM>
{
using ResultType = typename GCDLCMImpl<A, B, LCMImpl<A, B>, NameLCM>::ResultType;
static ResultType applyImpl(A a, B b)
{
using Int = typename NumberTraits::ToInteger<ResultType>::Type;
using Unsigned = make_unsigned_t<Int>;
/** It's tempting to use std::lcm function.
* But it has undefined behaviour on overflow.
* And assert in debug build.
* We need some well defined behaviour instead
* (example: throw an exception or overflow in implementation specific way).
*/
Unsigned val1 = abs<Int>(a) / boost::integer::gcd(Int(a), Int(b)); // NOLINT(clang-analyzer-core.UndefinedBinaryOperatorResult)
Unsigned val2 = abs<Int>(b);
/// Overflow in implementation specific way.
return ResultType(val1 * val2);
}
};
using FunctionLCM = BinaryArithmeticOverloadResolver<LCMImpl, NameLCM, false, false>;
}
REGISTER_FUNCTION(LCM)
{
factory.registerFunction<FunctionLCM>();
}
}
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