#include <math.h>#define NRANSI#include "nrutil.h"#define CON 1.4#define CON2 (CON*CON)#define BIG 1.0e30#define NTAB 10#define SAFE 2.0float dfridr(float (*func)(float), float x, float h, float *err){	int i,j;	float errt,fac,hh,**a,ans;	if (h == 0.0) nrerror("h must be nonzero in dfridr.");	a=matrix(1,NTAB,1,NTAB);	hh=h;	a[1][1]=((*func)(x+hh)-(*func)(x-hh))/(2.0*hh);	*err=BIG;	for (i=2;i<=NTAB;i++) {		hh /= CON;		a[1][i]=((*func)(x+hh)-(*func)(x-hh))/(2.0*hh);		fac=CON2;		for (j=2;j<=i;j++) {			a[j][i]=(a[j-1][i]*fac-a[j-1][i-1])/(fac-1.0);			fac=CON2*fac;			errt=FMAX(fabs(a[j][i]-a[j-1][i]),fabs(a[j][i]-a[j-1][i-1]));			if (errt <= *err) {				*err=errt;				ans=a[j][i];			}		}		if (fabs(a[i][i]-a[i-1][i-1]) >= SAFE*(*err)) break;	}	free_matrix(a,1,NTAB,1,NTAB);	return ans;}#undef CON#undef CON2#undef BIG#undef NTAB#undef SAFE#undef NRANSI