#include <math.h>#define NRANSI#include "nrutil.h"#define NMAX 6#define H 0.4#define A1 (2.0/3.0)#define A2 0.4#define A3 (2.0/7.0)float dawson(float x){	int i,n0;	float d1,d2,e1,e2,sum,x2,xp,xx,ans;	static float c[NMAX+1];	static int init = 0;	if (init == 0) {		init=1;		for (i=1;i<=NMAX;i++) c[i]=exp(-SQR((2.0*i-1.0)*H));	}	if (fabs(x) < 0.2) {		x2=x*x;		ans=x*(1.0-A1*x2*(1.0-A2*x2*(1.0-A3*x2)));	} else {		xx=fabs(x);		n0=2*(int)(0.5*xx/H+0.5);		xp=xx-n0*H;		e1=exp(2.0*xp*H);		e2=e1*e1;		d1=n0+1;		d2=d1-2.0;		sum=0.0;		for (i=1;i<=NMAX;i++,d1+=2.0,d2-=2.0,e1*=e2)			sum += c[i]*(e1/d1+1.0/(d2*e1));		ans=0.5641895835*SIGN(exp(-xp*xp),x)*sum;	}	return ans;}#undef NMAX#undef H#undef A1#undef A2#undef A3#undef NRANSI