euler.c

我自己写的数值分析课程设计的源代码

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

double f(double x,double y)
{
	return x+y;
}

double g(double x)
{
	return exp(x)+x*x/2;
}

void main()
{
	double a,b;
	double x,y;
	double ERR;
	double yr;
	int n;
	int i;
	double h;
	FILE *fout;

	fout=fopen("Euler.txt","a+");
	printf("Enter a,b,n:\n");
	scanf("%12lg%12lg%d",&a,&b,&n);

	fprintf(fout,"From %.12lg to %.12lg %d time(s)\n",a,b,n);

	h=(b-a)/n;
	x=0;
	y=1;
	yr=g(x);
	ERR=yr-y;
	fprintf(fout,"(x,y)=(%.12lg,%.12lg)\n ERR=%.12lg\n",x,y,ERR);

	for(i=1;i<=n;i++)
	{
		y+=h*f(x,y);
		x+=h;
		yr=g(x);
		ERR=yr-y;

		fprintf(fout,"(x,y)=(%.12lg,%.12lg)\n ERR=%.12lg\n",x,y,ERR);
	}


	fprintf(fout, "\n");
	fclose(fout);
}