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/* Copyright (c) 1986 Regents of the University of California */
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#ifndef lint
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static char SCCSid[] = "$SunId$ LBL";
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#endif
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/*
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* zeroes.c - compute roots for various equations.
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*
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* 8/19/85
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*/
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#define FTINY 1e-7
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int
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quadratic(r, a, b, c) /* find real roots of quadratic equation */
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double *r; /* roots in ascending order */
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double a, b, c;
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{
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double fabs(), sqrt();
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double disc;
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int first;
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if (a < -FTINY)
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first = 1;
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else if (a > FTINY)
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first = 0;
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else if (fabs(b) > FTINY) { /* solve linearly */
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r[0] = -c/b;
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return(1);
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} else
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return(0); /* equation is c == 0 ! */
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b *= 0.5; /* simplifies formula */
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disc = b*b - a*c; /* discriminant */
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if (disc < -FTINY*FTINY) /* no real roots */
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return(0);
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if (disc <= FTINY*FTINY) { /* double root */
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r[0] = -b/a;
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return(1);
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}
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disc = sqrt(disc);
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r[first] = (-b - disc)/a;
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r[1-first] = (-b + disc)/a;
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return(2);
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}
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