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//   Program electron
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#include <stdio.h>
#include "nxgraph.h"

//---- physical setting
#define Q          (-1.0)
#define M          (1.0)
#define dT         (1.0/256)
#define Eext       (1.0)
#define Bext       (1.0)

//---- graphic setting
#define WIN_WIDTH  (256)
#define WIN_HEIGHT (256)


//---- main function
int main(void)
{
  XEvent ev;
  NXOpenWindow("Electron motion in elemag field", WIN_WIDTH, WIN_HEIGHT );

  double qx=0.0, qy=0.0;
  double px=0.0, py=0.0;

  do{
    NXDrawPoint( WIN_WIDTH/2 + (int)(8*qx), - (int)(8*qy) );
    qx += px/M*dT;
    qy += py/M*dT;
    px += (Q*Eext + Q*Bext*py)*dT;
    py += (       - Q*Bext*px)*dT;
    NXCheckEvent( NX_NOWAIT, ev );
  }while( ev.type != KeyPress );

  NXCloseWindow();

  return(0);
}