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67 lines
1.4 KiB
C
67 lines
1.4 KiB
C
/*
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* matrix.c - 2D matrix operations
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*
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* Written 2010 by Werner Almesberger
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* Copyright 2010 by Werner Almesberger
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*/
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#include <assert.h>
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#include "matrix.h"
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void matrix_identity(struct matrix *m)
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{
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m->a[0][0] = m->a[1][1] = 1;
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m->a[0][1] = m->a[1][0] = 0;
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m->b[0] = m->b[1] = 0;
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}
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void matrix_invert(const double m[2][2], double res[2][2])
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{
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double det = m[0][0]*m[1][1]-m[0][1]*m[1][0];
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assert(res != (void *) m);
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res[0][0] = m[1][1]/det;
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res[0][1] = -m[0][1]/det;
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res[1][0] = -m[1][0]/det;
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res[1][1] = m[0][0]/det;
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}
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void matrix_mult(double a[2][2], double b[2][2], double res[2][2])
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{
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assert(res != a);
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assert(res != b);
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res[0][0] = a[0][0]*b[0][0]+a[0][1]*b[1][0];
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res[0][1] = a[0][0]*b[0][1]+a[0][1]*b[1][1];
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res[1][0] = a[1][0]*b[0][0]+a[1][1]*b[1][0];
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res[1][1] = a[1][0]*b[0][1]+a[1][1]*b[1][1];
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}
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void matrix_multv(const double v[2], double m[2][2], double res[2])
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{
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double tmp;
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tmp = v[0]*m[0][0]+v[1]*m[0][1];
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res[1] = v[0]*m[1][0]+v[1]*m[1][1];
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res[0] = tmp;
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}
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void matrix_copy(double from[2][2], double to[2][2])
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{
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to[0][0] = from[0][0];
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to[0][1] = from[0][1];
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to[1][0] = from[1][0];
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to[1][1] = from[1][1];
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}
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