int
gsl_sf_legendre_H3d_array(const int lmax, const double lambda, const double eta, double * result_array)
{
/* CHECK_POINTER(result_array) */
if(eta < 0.0 || lmax < 0) {
int ell;
for(ell=0; ell<=lmax; ell++) result_array[ell] = 0.0;
GSL_ERROR ("domain error", GSL_EDOM);
}
else if(eta > GSL_LOG_DBL_MAX) {
/* cosh(eta) is too big. */
int ell;
for(ell=0; ell<=lmax; ell++) result_array[ell] = 0.0;
GSL_ERROR ("overflow", GSL_EOVRFLW);
}
else if(lmax == 0) {
gsl_sf_result H0;
int stat = gsl_sf_legendre_H3d_e(0, lambda, eta, &H0);
result_array[0] = H0.val;
return stat;
}
else {
/* Not the most efficient method. But what the hell... it's simple.
*/
gsl_sf_result r_Hlp1;
gsl_sf_result r_Hl;
int stat_lmax = gsl_sf_legendre_H3d_e(lmax, lambda, eta, &r_Hlp1);
int stat_lmaxm1 = gsl_sf_legendre_H3d_e(lmax-1, lambda, eta, &r_Hl);
int stat_max = GSL_ERROR_SELECT_2(stat_lmax, stat_lmaxm1);
const double coth_eta = 1.0/tanh(eta);
int stat_recursion = GSL_SUCCESS;
double Hlp1 = r_Hlp1.val;
double Hl = r_Hl.val;
double Hlm1;
int ell;
result_array[lmax] = Hlp1;
result_array[lmax-1] = Hl;
for(ell=lmax-1; ell>0; ell--) {
double root_term_0 = sqrt(lambda*lambda + (double)ell*ell);
double root_term_1 = sqrt(lambda*lambda + (ell+1.0)*(ell+1.0));
Hlm1 = ((2.0*ell + 1.0)*coth_eta*Hl - root_term_1 * Hlp1)/root_term_0;
result_array[ell-1] = Hlm1;
if(!(Hlm1 < GSL_DBL_MAX)) stat_recursion = GSL_EOVRFLW;
Hlp1 = Hl;
Hl = Hlm1;
}
return GSL_ERROR_SELECT_2(stat_recursion, stat_max);
}
}
static VALUE rb_gsl_sf_legendre_H3d_e(VALUE obj,VALUE l, VALUE lambda, VALUE eta)
{
gsl_sf_result *rslt = NULL;
VALUE v;
// local variable "status" declared and set, but never used
//int status;
CHECK_FIXNUM(l);
Need_Float(lambda);
Need_Float(eta);
v = Data_Make_Struct(cgsl_sf_result, gsl_sf_result, 0, free, rslt);
/*status =*/ gsl_sf_legendre_H3d_e(FIX2INT(l), NUM2DBL(lambda), NUM2DBL(eta), rslt);
return v;
}
double gsl_sf_legendre_H3d(const int l, const double lambda, const double eta)
{
EVAL_RESULT(gsl_sf_legendre_H3d_e(l, lambda, eta, &result));
}
