// Calculation Program for displaying eye shaped curves (e), 13 Sep., 2008



// Equation of the curve: (1+b*y*y)-1/(1+c*x*x)=exp(a)



// file name: eye_shaped_curves_e.c



#include< stdio.h>

#include< math.h>



void main(void)

{

	double x,y,a,amax,amin,da,b,c;

	int i,imax,n,nmax,j,m;

	double xmax,xmin,dx;

	double xx[2005],yy[10][1005];// Take care of the upper limit of storage memory capacitance.



	FILE *fp;



// Setting of the constants

	b=.8;

	c=1;



        amax=0.64;// maximum value of a

	amin=-2;// minimum value of a

	da=(amax-amin)/3;// interval among parameter values of a

	 

// Setting of the other parameters

	xmax=2.1;// maximum value of x

	xmin=-xmax;// minimum value of x

	dx=(xmax-xmin)/420;// plotting interval of x



	i=0;

	n=0;



// execution of calculation

	for(a=amin;a<=amax;a=a+da)

		{

		n++;

		i=0;



		for(x=-xmax;x<=xmax;x=x+dx)

			{

			i++;

			xx[i]=x;



			if(a<0&&x*x>exp(a)/(c*(1-exp(a))))

			{

				y=0;

			}

			else

			{

				y=sqrt((exp(a)-1+1/(1+c*x*x))/b);

			}



			yy[n][i]=y;



			printf("i=%d,n=%d,a=%f,x=%f,y=%f\n",i,n,a,b,c,x,y);

			}

		}



	imax=i;

	nmax=n;

	j=0;



	for(i=imax+1;i<=2*imax;i++)

		{

		j++;

		m=imax-j;



		xx[i]=xx[m];



		for(n=1;n<=nmax;++n)

			{

			yy[n][i]=-yy[n][m];

			}

		}



// writing the calculated coordinates data of the curve into a textfile

	fp=fopen("eye-shaped curve.txt","w");

	if(fp==NULL)

		{

		printf("FILE OPEN ERROR\n");

		}

	else

		{

		for(i=1;i<=2*imax-1;i++)

			{

			fprintf(fp,"%f,%f,%f,%f,%f\n",xx[i],yy[1][i],yy[2][i],yy[3][i],yy[4][i]);

			}

		fflush(fp);

		fclose(fp);

		}

	printf("end\n");

}// the end of the program