// Calculation Program for displaying a single rectangle, 22(Sun.) June, 2008



// Equation of rectangle：exp(x*x-bx)+exp(y*y-c*y)=a*exp(a*a), where the values of a, b and c are arbitrary real numbers.



// file name: rectangle_E.c



#include< stdio.h>

#include< math.h>



void main(void)

{

	double x,y,a,b,c;

	int i,imax,j,m;

	double xmin,xmax,dx;

	double xx[10001],yy[10001];// Take care of the upper limit of storage memory capacitance.



	FILE *fp;



// Setting of the constants

        a=1;

	b=100;

	c=100;



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



// Setting of the other parameters

	// xmin and xmax represent the two point at which a rectangle cuts the x-axis.

	xmin=b-sqrt(b*b+log(2*exp(a*a)-1));

	xmax=b+sqrt(b*b+log(2*exp(a*a)-1));

	dx=(xmax-xmin)/4000;// plotting interval of x



// Execution of calculation

	i=0;

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

		{

		i++;



		xx[i]=x;



		y=c+sqrt(c*c+log(2*exp(a*a)-exp(x*x-2*b*x)));

		yy[i]=y;

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

		}

	imax=i;

	j=0;



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

		{

		j++;

		m=imax-j;



		xx[i]=xx[m];

		x=xx[i];

		yy[i]=c-sqrt(c*c+log(2*exp(a*a)-exp(x*x-2*b*x)));

		}



	xx[2*imax]=xx[1];

	x=xx[2*imax];

	y=c+sqrt(c*c+log(2*exp(a*a)-exp(x*x-2*b*x)));

	yy[2*imax]=y;



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

	fp=fopen("rectangle.txt","w");

	if(fp==NULL)

		{

		printf("FILE OPEN ERROR\n");

		}

	else

		{

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

			{

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

			}

		fflush(fp);

		fclose(fp);

		}

	printf("end\n");

}// the end of the program