Real Argument
- Function: double gsl_sf_dilog (double x)
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- Function: int gsl_sf_dilog_e (double x, gsl_sf_result * result)
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These routines compute the dilogarithm for a real argument. In Lewin's
notation this is Li_2(x), the real part of the dilogarithm of a
real x. It is defined by the integral representation
Li_2(x) = - \Re \int_0^x ds \log(1-s) / s.
Note that \Im(Li_2(x)) = 0 for
x <= 1, and -\pi\log(x) for x > 1.