9fpts.c

来自「文件中集合了常用的一些算法的C实现」· C语言 代码 · 共 30 行

  #include "math.h"
  double fpts(a,b,eps,d,f)
  double a,b,eps,d,(*f)();
  { double h,t[2],f0,f1,t0,z;
    void ppp();
    h=b-a; t[0]=0.0;
    f0=(*f)(a); f1=(*f)(b);
    t0=h*(f0+f1)/2.0;
    ppp(a,b,h,f0,f1,t0,eps,d,t,f);
    z=t[0]; return(z);
  }

  static void ppp(x0,x1,h,f0,f1,t0,eps,d,t,ff)
  double x0,x1,h,f0,f1,t0,eps,d,t[],(*ff)();
  { double x,f,t1,t2,p,g,eps1;
    x=x0+h/2.0; f=(*ff)(x);
    t1=h*(f0+f)/4.0; t2=h*(f+f1)/4.0;
    p=fabs(t0-(t1+t2));
    if ((p<eps)||(h/2.0<d))
      { t[0]=t[0]+(t1+t2); return;}
    else
      { g=h/2.0; eps1=eps/1.4;
        ppp(x0,x,g,f0,f,t1,eps1,d,t,ff);
        ppp(x,x1,g,f,f1,t2,eps1,d,t,ff);
        return;
      }
  }