\item The macro-processor transforms a MOD file with macro-commands into a MOD file without macro-commands (doing text expansions/inclusions) and then feeds it to the Dynare parser
\item The key point to understand is that the macro-processor only does \textbf{text substitution} (like the C preprocessor or the PHP language)
\item In most cases, directives occupy exactly one line of text. In case of need, two anti-slashes (\verb+\\+) at the end of the line indicates that the directive is continued on the next line.
\end{itemize}
\end{frame}
\begin{frame}
\frametitle{Variables}
\begin{itemize}
\item The macro processor maintains its own list of variables (distinct of model variables and of MATLAB/Octave variables)
\item Macro-variables can be of four types:
\begin{itemize}
\item integer
\item character string (declared between \textit{double} quotes)
\item array of integers
\item array of strings
\end{itemize}
\item No boolean type:
\begin{itemize}
\item false is represented by integer zero
\item true is any non-null integer
\end{itemize}
\end{itemize}
\end{frame}
\begin{frame}[fragile=singleslide]
\frametitle{Macro-expressions (1/2)}
It is possible to construct macro-expressions, using standard operators.
\item integer ranges: \texttt{1:4} is equivalent to integer array \texttt{[1,2,3,4]}
\end{itemize}
\end{block}
\begin{block}{Operators on character strings}
\begin{itemize}
\item comparison operators: \texttt{== !=}
\item concatenation: \texttt{+}
\item extraction of substrings: if \texttt{s} is a string, then one can write \texttt{s[3]} or \texttt{s[4:6]}
\end{itemize}
\end{block}
\end{frame}
\begin{frame}[fragile=singleslide]
\frametitle{Macro-expressions (2/2)}
\begin{block}{Operators on arrays}
\begin{itemize}
\item dereferencing: if \texttt{v} is an array, then \texttt{v[2]} is its $2^{\textrm{nd}}$ element
\item concatenation: \texttt{+}
\item difference \texttt{-}: returns the first operand from which the elements of the second operand have been removed
\item extraction of sub-arrays: \textit{e.g.}\texttt{v[4:6]}
\item testing membership of an array: \texttt{in} operator \\ (example:
\texttt{"b" in ["a", "b", "c"]} returns \texttt{1})
\end{itemize}
\end{block}
Macro-expressions can be used at two places:
\begin{itemize}
\item inside macro directives, directly
\item in the body of the MOD file, between an at-sign and curly braces (like \verb+@{expr}+): the macro processor will substitute the expression with its value
\end{itemize}
\end{frame}
\begin{frame}[fragile=singleslide]
\frametitle{Define directive}
The value of a macro-variable can be defined with the \verb+@#define+ directive.
