// Calculation Program for displaying a single egg-shaped-curve, 19(Wed) March, 2008
// In the case of a=1, b=0.8,  When b=0, the curve is a circle.
// file name: egg_curve_1b_E.c

#include< stdio.h>
#include< math.h>

void main(void)
{
	double x,y,a,b,pi;// pi is the Pi.
	double t,dt;
	int i,imax;
	double xx[10001],yy[10001];// Take care of the upper limit of storage memory capacitance.

	FILE *fp;

// Setting of the constants
        pi=3.1415927;
        a=1.0;
	b=.7;

	printf("a=%f\n\n",a);

// Setting of the other parameters
	dt=pi/4000;// plotting interval of intermediate variable t

	i=0;

// execution of calculation
	for(t=-pi;t<=pi;t=t+dt)
	{
		i++;

		x=a/2-b/4+(a/2)*cos(t)+(b/4)*cos(t)*cos(t);
		y=(a/2-b/4+(b/4)*cos(t))*sin(t);
		xx[i]=x;
		yy[i]=y;

		printf("i=%d,x=%f,y=%f\n",i,x,y);
	}

	imax=i;

// writing the calculated coordinates data of the curve into a textfile
	fp=fopen("egg_shaped_curve.txt","w");

	if(fp==NULL)
	{
		printf("FILE OPEN ERROR\n");
	}
	else
	{
		for(i=1;i<=imax;i++)
		{
			fprintf(fp,"%f,%f\n",xx[i],yy[i]);
		}

	fflush(fp);
	fclose(fp);
	}

	printf("end\n");
}// the end of the program