— Function: double gsl_sf_Shi (double x)
— Function: int gsl_sf_Shi_e (double x, gsl_sf_result * result)

These routines compute the integral Shi(x) = \int_0^x dt \sinh(t)/t.

— Function: double gsl_sf_Chi (double x)
— Function: int gsl_sf_Chi_e (double x, gsl_sf_result * result)

These routines compute the integral Chi(x) := \Re[ \gamma_E + \log(x) + \int_0^x dt (\cosh[t]-1)/t] , where \gamma_E is the Euler constant (available as the macro M_EULER).