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/* Copyright (c) 1986 Regents of the University of California */ |
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|
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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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/* |
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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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|
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|
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#include <math.h> |
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|
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#include "fvect.h" |
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|
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|
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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 disc; |
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int first; |
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|
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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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|
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b *= 0.5; /* simplifies formula */ |
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|
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disc = b*b - a*c; /* discriminant */ |
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|
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if (disc < -FTINY*FTINY) /* no real roots */ |
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return(0); |
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|
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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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|
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disc = sqrt(disc); |
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|
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r[first] = (-b - disc)/a; |
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r[1-first] = (-b + disc)/a; |
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|
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return(2); |
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} |
