\subsection{$+$}
\label{labplus}
\noindent Name: \textbf{$+$}\\
\phantom{aaa}addition function\\[0.2cm]
\noindent Library names:\\
\verb|   sollya_obj_t sollya_lib_add(sollya_obj_t, sollya_obj_t)|\\
\verb|   sollya_obj_t sollya_lib_build_function_add(sollya_obj_t, sollya_obj_t)|\\
\verb|   #define SOLLYA_ADD(x,y) sollya_lib_build_function_add((x), (y))|\\[0.2cm]
\noindent Usage: 
\begin{center}
\emph{function1} \textbf{$+$} \emph{function2} : (\textsf{function}, \textsf{function}) $\rightarrow$ \textsf{function}\\
\emph{interval1} \textbf{$+$} \emph{interval2} : (\textsf{range}, \textsf{range}) $\rightarrow$ \textsf{range}\\
\emph{interval1} \textbf{$+$} \emph{constant} : (\textsf{range}, \textsf{constant}) $\rightarrow$ \textsf{range}\\
\emph{interval1} \textbf{$+$} \emph{constant} : (\textsf{constant}, \textsf{range}) $\rightarrow$ \textsf{range}\\
\end{center}
Parameters: 
\begin{itemize}
\item \emph{function1} and \emph{function2} represent functions
\item \emph{interval1} and \emph{interval2} represent intervals (ranges)
\item \emph{constant} represents a constant or constant expression
\end{itemize}
\noindent Description: \begin{itemize}

\item \textbf{$+$} represents the addition (function) on reals. 
   The expression \emph{function1} \textbf{$+$} \emph{function2} stands for
   the function composed of the addition function and the two
   functions \emph{function1} and \emph{function2}.

\item \textbf{$+$} can be used for interval arithmetic on intervals
   (ranges). \textbf{$+$} will evaluate to an interval that safely
   encompasses all images of the addition function with arguments varying
   in the given intervals.  Any combination of intervals with intervals
   or constants (resp. constant expressions) is supported. However, it is
   not possible to represent families of functions using an interval as
   one argument and a function (varying in the free variable) as the
   other one.
\end{itemize}
\noindent Example 1: 
\begin{center}\begin{minipage}{15cm}\begin{Verbatim}[frame=single]
> 1 + 2;
3
\end{Verbatim}
\end{minipage}\end{center}
\noindent Example 2: 
\begin{center}\begin{minipage}{15cm}\begin{Verbatim}[frame=single]
> x + 2;
2 + x
\end{Verbatim}
\end{minipage}\end{center}
\noindent Example 3: 
\begin{center}\begin{minipage}{15cm}\begin{Verbatim}[frame=single]
> x + x;
x * 2
\end{Verbatim}
\end{minipage}\end{center}
\noindent Example 4: 
\begin{center}\begin{minipage}{15cm}\begin{Verbatim}[frame=single]
> diff(sin(x) + exp(x));
cos(x) + exp(x)
\end{Verbatim}
\end{minipage}\end{center}
\noindent Example 5: 
\begin{center}\begin{minipage}{15cm}\begin{Verbatim}[frame=single]
> [1;2] + [3;4];
[4;6]
> [1;2] + 17;
[18;19]
> 13 + [-4;17];
[9;30]
\end{Verbatim}
\end{minipage}\end{center}
See also: \textbf{$-$} (\ref{labminus}), \textbf{$*$} (\ref{labmult}), \textbf{/} (\ref{labdivide}), \textbf{$\mathbf{\hat{~}}$} (\ref{labpower})
