# 2.11BSD#431 - /usr/src/usr.lib/libplot/hp2648/arc.c

##### Functions

    arc               X
    cross_product     X

       1: /*
       2:  * Copyright (c) 1980 Regents of the University of California.
       3:  * All rights reserved.  The Berkeley software License Agreement
       4:  * specifies the terms and conditions for redistribution.
       5:  */
       6:
       7: #ifndef lint
       8: static char sccsid[] = "@(#)arc.c	5.1 (Berkeley) 5/7/85";
       9: #endif not lint
      10:
      11: #include "hp2648.h"
      12:
      13: arc(xcent,ycent,xbeg,ybeg,xend,yend)
      14: int xcent,ycent,xbeg,ybeg,xend,yend;
      15: {
      16:     double costheta,sintheta,x,y,xn,r;
      17:     double x1,y1,x2,y2;
      18:     int xi,yi,crosspflag,crossp;
      19:
      20:     r = (xcent-xbeg)*(xcent-xbeg)+(ycent-ybeg)*(ycent-ybeg);
      21:     r = pow(r,0.5);
      22:     if(r<1){
      23:         point(xcent,ycent);
      24:         return;
      25:     }
      26:     sintheta = 1.0/r;
      27:     costheta = pow(1-sintheta*sintheta,0.5);
      28:     xi = x = xbeg-xcent;
      29:     yi = y = ybeg-ycent;
      30:     x1 = xcent;
      31:     y1 = ycent;
      32:     x2 = xend;
      33:     y2 = yend;
      34:     crosspflag = 0;
      35:     do {
      36:         crossp = cross_product(x1,y1,x2,y2,x,y);
      37:         if(crossp >0 && crosspflag == 0) crosspflag = 1;
      38:         point(xcent+xi,ycent+yi);
      39:         xn = x;
      40:         xi = x = x*costheta + y*sintheta;
      41:         yi = y = y*costheta - xn*sintheta;
      42:     } while( crosspflag == 0 || crossp >0);
      43: }
      44:
      45: cross_product(x1,y1,x2,y2,x3,y3)
      46: double x1,x2,x3,y1,y2,y3;
      47: {
      48:     double z,a,b;
      49:     a = (y3-y2)*(x2-x1);
      50:     b = (x3-x2)*(y2-y1);
      51:     z = a-b;
      52:     if(z<0) return(-1);
      53:     if(z>0) return(1);
      54:     return(0);
      55: }

#### Defined functions

arc defined in line 13; never used
cross_product defined in line 45; used 1 times

- in line 36

#### Defined variables

sccsid defined in line 8; never used

Last modified: 1987-02-18 Generated: 2016-12-26 | Generated by src2html V0.67 page hit count: 783 |