3 The functions described in this section are declared in the header file
12 @subsection Real Argument
14 @deftypefun double gsl_sf_dilog (double @var{x})
15 @deftypefunx int gsl_sf_dilog_e (double @var{x}, gsl_sf_result * @var{result})
16 These routines compute the dilogarithm for a real argument. In Lewin's
17 notation this is @math{Li_2(x)}, the real part of the dilogarithm of a
18 real @math{x}. It is defined by the integral representation
19 @math{Li_2(x) = - \Re \int_0^x ds \log(1-s) / s}.
20 Note that @math{\Im(Li_2(x)) = 0} for @c{$x \le 1$}
21 @math{x <= 1}, and @math{-\pi\log(x)} for @math{x > 1}.
23 Note that Abramowitz & Stegun refer to the Spence integral
24 @math{S(x)=Li_2(1-x)} as the dilogarithm rather than @math{Li_2(x)}.
27 @node Complex Argument
28 @subsection Complex Argument
31 @deftypefun int gsl_sf_complex_dilog_e (double @var{r}, double @var{theta}, gsl_sf_result * @var{result_re}, gsl_sf_result * @var{result_im})
32 This function computes the full complex-valued dilogarithm for the
33 complex argument @math{z = r \exp(i \theta)}. The real and imaginary
34 parts of the result are returned in @var{result_re}, @var{result_im}.