// Calculation Program for calculation of an apple shaped curve，Mar. 29, 2010.

// file name: apple.c

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

void main(void)
{
	double a,pi;// a is a constant and pi is the Pi.
	double b;// a constant
	double p, q;// constants
	double t,dt;// an intermediate variable and its increment
	double R;// an intermediate variable
	double tmin,tmax;// the minimum and maximum values of the intermediate variable t
	int i,imax;
	double xx[10001],yy[10001];// Take care of the upper limit of storage memory capacitance.

	FILE *fp;

// setting of the constant
	pi=3.14159265;
	a=1.0;
	b=1.2;
	p=0.15;
	q=0.08;

// setting of the other parameters
	tmin=-pi/2;
	tmax=3*pi/2;
	dt=(tmax-tmin)/4000;// plotting interval of t

// execution of calculation
	i=0;
	for(t=tmin;t<=tmax+dt;t=t+dt)
		{
		i++;

		R=a*(1-sin(t));

		xx[i]=R*cos(t)*exp(-p*(t-pi/2)*(t-pi/2));
		yy[i]=b*R*sin(t)*exp(-q*(t-pi/2)*(t-pi/2));

		printf("i=%d,x=%f,y=%f\n",i,xx[i],yy[i]);
		}
	imax=i;

// writing the calculated coordinates data of the apple shaped curve into a textfile
	fp=fopen("apple.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

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