erchongjifen.rar_二重积分

/*二重积分的表达形式 其中积分区域为：x=1 y=1 y=-4/5*x+29/5 积分函数为：　　f(x,y)=1　 */ #include <stdio.h> #include <math.h> static double simp1(double x,double eps,void (*s)(double x,double y[2]),double(*f)(double x,double y)) { int n,i; double y[2],h,d,t1,yy,t2,g,ep,g0; n=1; (*s)(x,y); h=0.5*(y[1]-y[0]); d=fabs(h*2.0e-06); t1=h*((*f)(x,y[0])+(*f)(x,y[1])); ep=1.0+eps; g0=1.0e+35; while(((ep>=eps)&&(fabs(h)>d))||(n<16)) { yy=y[0]-h; t2=0.5*t1; for(i=1;i<=n;i++) { yy=yy+2.0*h; t2=t2+h*(*f)(x,yy); } g=(4.0*t2-t1)/3.0; ep=fabs(g-g0)/(1.0+fabs(g)); n=n+n; g0=g; t1=t2; h=0.5*h; } return(g); } double sim2(double a,double b,double eps,void(*ss)(double x,double y[2]),double(*f)(double x,double y)) { int n,j; double h,d,s1,s2,t1,x,t2,g,s,s0,ep; n=1; h=0.5*(b-a); d=fabs((b-a)*1.0e-06); s1=simp1(a,eps,ss,f); s2=simp1(b,eps,ss,f); t1=h*(s1+s2); s0=1.0e+35; ep=1.0+eps; while(((ep>=eps)&&(fabs(h)>d))||(n<16)) { x=a-h; t2=0.5*t1; for(j=1;j<=n;j++) { x=x+2.0*h; g=simp1(x,eps,ss,f); t2=t2+h*g; } s=(4.0*t2-t1)/3.0; ep=fabs(s-s0)/(1.0+fabs(s)); n=n+n; s0=s; t1=t2; h=h*0.5; } return(s); } void main() { double a,b,eps,s,sim2f(double,double); void sim2s(double,double[]); a=1.0; b=6.0; eps=0.001; s=sim2(a,b,eps,sim2s,sim2f); printf("\n"); printf("s=%e\n",s); printf("\n"); } void sim2s(double x,double y[2]) { y[0]=1; y[1]=-4/5*x+29/5; return; } double sim2f(double x,double y) { double z; z=1.0; return(z); }