28 lines
543 B
C
28 lines
543 B
C
#include <math.h>
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struct circle {
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double c;
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double s;
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};
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void approx_turn_update(double turn, struct circle* ret)
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{
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static const double a = 8 * M_SQRT2 / 3 - 3;
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static const double b = 4 - 8 * M_SQRT2 / 3;
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double p = turn * (b * turn * turn + a);
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double q = p * p;
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double r = 1 + q;
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double c = (1 - q) / r, s = 2 * p / r;
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ret->c = c * c - s * s;
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ret->s = 2 * c * s;
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}
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void turn_update(double turn, struct circle* ret)
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{
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double arg = M_PI * turn;
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ret->c = cos(arg);
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ret->s = sin(arg);
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}
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