say something about shields

diff --git a/mtask.io.tex b/mtask.io.tex
index 07eb3ea..b896da0 100644 (file)
--- a/mtask.io.tex
+++ b/mtask.io.tex
@@ -32,7 +32,7 @@ class assign v where
 One way of storing data in \gls{mTask}-\glspl{Task} is using \glspl{SDS}.
 \glspl{SDS} serve as variables in \gls{mTask} and maintain their value across
 executions.  \glspl{SDS} can be used by multiple \glspl{Task} and can be used
-to share data.  The classes associated with \glspl{SDS} are listed in
+to share data. The classes associated with \glspl{SDS} are listed in
 Listing~\ref{lst:sdsclass}. The \CI{Main} type is introduced to box an
 \gls{mTask} and make it recognizable by the type system by separating programs
 and decorations such as \glspl{SDS}.
@@ -45,3 +45,36 @@ and decorations such as \glspl{SDS}.
 class sds v where
   sds :: ((v t Upd)->In t (Main (v c s))) -> (Main (v c s)) | ...
 \end{lstlisting}
+
+In the \emph{Arduino} ecosystem, shields are available to plug into the
+microcontroller and add functionality. These shields range from Bluetooth,
+WiFi, Ethernet, LoRa, LCD screens and much more. Often the functionality
+available in these shields is housed in a \gls{C++} class. This functionality
+is ported using little work to \gls{mTask} by just creating a corresponding
+class with the same functions. As an example, Listing~\ref{lst:lcd} shows parts
+of the \gls{LCD} class as an \gls{mTask} class functions and as
+Listing~\ref{lst:lcdc} shown the corresponding \emph{Arduino} class functions.
+
+\begin{lstlisting}[label={lst:lcd},%
+       caption={Adding the \gls{LCD} to the \gls{mTask} language}]
+:: LCD = ...
+
+class lcd v where
+  begin          :: (v LCD Expr) (v Int p) (v Int q) -> v () Expr
+  ...
+  scrollLeft     :: (v LCD Expr) -> v () Expr
+  scrollRight    :: (v LCD Expr) -> v () Expr
+  ...
+\end{lstlisting}
+
+\begin{lstlisting}[language=C++,label={lst:lcdc},%
+       caption={Functions from the \gls{Arduino} \gls{LCD} library}]
+class LiquidCrystal {
+public:
+  void begin(uint8_t cols, uint8_t rows);
+  ...
+  void scrollDisplayLeft();
+  void scrollDisplayRight();
+  ...
+}
+\end{lstlisting}