\subsection{erf}
\label{laberf}
\noindent Name: \textbf{erf}\\
\phantom{aaa}the error function.\\[0.2cm]
\noindent Library names:\\
\verb|   sollya_obj_t sollya_lib_erf(sollya_obj_t)|\\
\verb|   sollya_obj_t sollya_lib_build_function_erf(sollya_obj_t)|\\
\verb|   #define SOLLYA_ERF(x) sollya_lib_build_function_erf(x)|\\[0.2cm]
\noindent Description: \begin{itemize}

\item \textbf{erf} is the error function defined by:
   $$\mathrm{erf}(x) = \frac{2}{\sqrt{\pi}} \int_0^x e^{-t^2} {\rm d}t.$$

\item It is defined for every real number x.
\end{itemize}
See also: \textbf{erfc} (\ref{laberfc}), \textbf{exp} (\ref{labexp})
