double complex secondPart(const int l, const double gamma, const double Lamda, const double qSqur, int * const rstatus)
{
int s1 = 0, s2 = 0;
double complex secondPartInt = 0+0*I;
if(l != 0){
secondPartInt = 0.0;
}
else{
//Integration method.
/*
secondPartInt = spheHarm(0, 0, 0, 0, &s1) * gamma * pow(M_PI,3.0/2.0)
* ( 2 * qSqur * sndInteFunc(Lamda, qSqur, &s2)
-2 * exp(Lamda * qSqur)/sqrt(Lamda));
*/
//Arithmetic method.
double inteCore = 0.0;
if(qSqur > 0){
//Dawson function for qSqur>0
inteCore = 4 * sqrt(qSqur) * exp(Lamda * qSqur) * gsl_sf_dawson(sqrt(Lamda * qSqur));
}
else if(fabs(qSqur) < DBL_EPSILON) {
inteCore = 0;
}
else if(qSqur < 0){
//Error function for qSqur<0
inteCore = -2 * sqrt(M_PI) * sqrt( - qSqur) * erf( sqrt( - Lamda * qSqur) );
}
secondPartInt = spheHarm(0, 0, 0, 0, &s1) * gamma * pow(M_PI,3.0/2.0)
* ( inteCore - 2 * exp(Lamda * qSqur)/sqrt(Lamda));
}
*rstatus = s1 + s2;
//printf("Lamda=%lf,qSqur = %.4f\nsecondPartInt = %.24f \n", Lamda, qSqur, secondPartInt);
return secondPartInt;
}
static VALUE Dawson_dawson(VALUE self, VALUE x) {
return rb_float_new(gsl_sf_dawson(NUM2DBL(x)));
}
/**
* C++ version of gsl_sf_dawson().
* Dawson's integral:
*
* Exp[-x^2] Integral[ Exp[t^2], {t,0,x}]
* @param x A real number
* @return The integral
*/
inline double dawson( double x ){ return gsl_sf_dawson( x ); }
