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50 lines
1.1 KiB
50 lines
1.1 KiB
#pragma once
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#include <cmath>
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namespace md5::math {
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constexpr double PI = 3.14159265358979323846264338327950;
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constexpr double pow(double x, int n) {
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double res = 1;
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for (int i = 0; i < n; ++i) {
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res *= x;
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}
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return res;
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}
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constexpr double factorial(int n) {
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double res = 1;
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for (int i = 2 ; i <= n ; ++i) {
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res *= i;
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}
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return res;
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}
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/// Calculate sin(x) value with Maclaurin series.
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constexpr double sin_core(double x) {
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double res = x;
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for (int i = 1; i < 80; ++i) {
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const int n = i * 2 + 1;
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const int sign = (i & 1) ? -1 : 1;
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res += sign * pow(x, n) / factorial(n);
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}
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return res;
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}
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/// Calculate the sin(x) value in radians.
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constexpr double sin(double x) {
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x = ::std::fmod(x, 2 * PI); // -2PI < x < 2PI
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if (::std::abs(x) > PI) {
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x -= ((x > 0) ? 2 : -2) * PI; // -PI < x < PI
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}
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if (::std::abs(x) > PI / 2) {
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x = ((x > 0) ? 1 : -1) * PI - x; // -PI / 2 < x < PI / 2
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}
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return sin_core(x); // closer to 0 for better accuracy
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}
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} // namespace md5::math
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