smoother.h

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/* 
* Copyright (C) 2020-2026 MEmilio
*
* Authors: Martin J. Kuehn, Daniel Abele
*
* Contact: Martin J. Kuehn <Martin.Kuehn@DLR.de>
*
* 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.
*/
#ifndef MIO_MATH_SMOOTHER_H
#define MIO_MATH_SMOOTHER_H
 
#include "memilio/config.h"
#include "memilio/math/eigen.h"
 
#include <cmath>
#include <numbers>
 
namespace mio
{
 
template <typename FP>
inline FP smoother_cosine(FP x, FP xleft, FP xright, FP yleft, FP yright)
{
    using std::cos;
 
    if (x <= xleft) {
        return yleft;
    }
    if (x >= xright) {
        return yright;
    }
 
    return 0.5 * (yleft - yright) * cos(std::numbers::pi_v<ScalarType> / (xright - xleft) * (x - xleft)) +
           0.5 * (yleft + yright);
}
 
template <typename FP, class LeftExpr, class RightExpr>
auto smoother_cosine(FP x, FP xleft, FP xright, const Eigen::MatrixBase<LeftExpr>& yleft_expr,
                     const Eigen::MatrixBase<RightExpr>& yright_expr)
{
    return yleft_expr.binaryExpr(yright_expr, [=](auto yleft, auto yright) {
        return smoother_cosine<FP>(x, xleft, xright, yleft, yright);
    });
}
 
} // namespace mio
 
#endif // MIO_MATH_SMOOTHER_H