邝斌的ACM模板（自适应 simpson 积分）

double simpson(double a,double b)
{
double c = a + (b-a)/2;
return (F(a) + 4*F(c) + F(b))*(b-a)/6;
}
double asr(double a,double b,double eps,double A)
{
double c = a + (b-a)/2;
double L = simpson(a,c), R = simpson(c,b);
if(fabs(L + R - A) <= 15*eps)return L + R + (L + R - A)/15.0;
return asr(a,c,eps/2,L) + asr(c,b,eps/2,R);
}
double asr(double a,double b,double eps)
{
return asr(a,b,eps,simpson(a,b));
}