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/*
* Copyright (C) 2012 Open Source Robotics Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
#include "ignition/math/Helpers.hh"
namespace ignition
{
namespace math
{
inline namespace IGNITION_MATH_VERSION_NAMESPACE
{
/////////////////////////////////////////////
PairOutput Pair(const PairInput _a, const PairInput _b)
{
// Store in 64bit local variable so that we don't overflow.
uint64_t a = _a;
uint64_t b = _b;
// Szudzik's function
return _a >= _b ?
static_cast<PairOutput>(a * a + a + b) :
static_cast<PairOutput>(a + b * b);
}
/////////////////////////////////////////////
std::tuple<PairInput, PairInput> Unpair(const PairOutput _key)
{
// Accurate 64-bit integer sqrt
// From https://stackoverflow.com/a/18501209
//
// \todo: Remove this ifdef and use the "0x1p-20" version when c++17
// is used. All platforms should then support the "p" literal.
//
// Note that the of Hexadecimal floats is failing in some Linux g++
// compilers from 6.x/7.x series. The native support for C++ is defined
// in C++17 See https://bugzilla.redhat.com/show_bug.cgi?id=1321986
#if (__cplusplus < 201703L)
uint64_t sqrt = static_cast<uint64_t>(std::sqrt(_key) -9.53674e-07);
#else
uint64_t sqrt = static_cast<uint64_t>(std::sqrt(_key) - 0x1p-20);
#endif
if (2 * sqrt < _key - sqrt * sqrt)
sqrt++;
uint64_t sq = sqrt * sqrt;
return ((_key - sq) >= sqrt) ?
std::make_tuple(static_cast<PairInput>(sqrt),
static_cast<PairInput>(_key - sq - sqrt)) :
std::make_tuple(static_cast<PairInput>(_key - sq),
static_cast<PairInput>(sqrt));
}
}
}
}
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