simp.c

计算方法中的常用程序

  #include "math.h"
  double simp(a,b,eps,f)
  double a,b,eps,(*f)();
  { int n,k;
    double h,t1,t2,s1,s2,ep,p,x;
    n=1; h=b-a;
    t1=h*((*f)(a)+(*f)(b))/2.0;
    s1=t1;
    ep=eps+1.0;
    while (ep>=eps)
      { p=0.0;
        for (k=0;k<=n-1;k++)
          { x=a+(k+0.5)*h;
            p=p+(*f)(x);
          }
        t2=(t1+h*p)/2.0;
        s2=(4.0*t2-t1)/3.0;
        ep=fabs(s2-s1);
        t1=t2; s1=s2; n=n+n; h=h/2.0;
      }
    return(s2);
  }