49 lines
1.2 KiB
C++
49 lines
1.2 KiB
C++
#include <cmath>
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#include <complex>
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#include "spline.h"
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using std::floor;
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using std::complex;
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const complex<double> I(0.0, 1.0);
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spline4::spline4() {}
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double spline4::operator()(double x) const {
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if (0.0 < x && x < 1.0)
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return 1.0 / 6.0 * x * x * x;
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else if (1.0 <= x && x < 2.0)
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return 2.0 / 3.0 + (-2.0 + (2.0 - 1.0 / 2.0 * x) * x) * x;
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else if (2.0 <= x && x < 3.0)
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return -22.0 / 3.0 + (10.0 + (-4.0 + 1.0 / 2.0 * x) * x) * x;
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else if (3.0 <= x && x < 4.0)
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return 32.0 / 3.0 + (-8.0 + (2.0 - 1.0 / 6.0 * x) * x) * x;
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else
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return 0.0;
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}
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double spline4::diff(double x) const {
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if (0.0 < x && x < 1.0)
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return 1.0 / 2.0 * x * x;
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else if (1.0 <= x && x < 2.0)
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return -2.0 + (4.0 - 3.0 / 2.0 * x) * x;
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else if (2.0 <= x && x < 3.0)
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return 10.0 + (-8.0 + 3.0 / 2.0 * x) * x;
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else if (3.0 <= x && x < 4.0)
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return -8.0 + (4.0 - 1.0 / 2.0 * x) * x;
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else
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return 0.0;
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}
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complex<double> spline4::factor(double m, double K) const {
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const double m_over_K = m / K;
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complex<double> denom = 0.0;
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for (double k = 0.0; k <= order - 2.0; k++)
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denom += operator()(k + 1.0) * exp(2.0 * M_PI * I * m_over_K * k);
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return exp(2.0 * M_PI * I * (order - 1.0) * m_over_K) / denom;
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}
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