instance isExpr Expr
\end{lstlisting}
-\section{Semantics}
-The \gls{C}-backend of the \gls{mTask}-system has an engine that is generated
-alongside the code for the \glspl{Task}. This engine will execute the
-\glspl{mTask} according to certain rules and semantics.
-\glspl{mTask} do not behave like functions but more like
-\gls{iTasks}-\glspl{Task}. An \gls{mTask} is queued when either his timer runs
-out or when it is started by another \gls{mTask}. When an \gls{mTask} is
-queued it does not block the execution but it will return immediately while
-the actual \gls{Task} will be executed some time in the future.
-
-The \gls{iTasks}-backend simulates the \gls{C}-backend and thus uses the same
-semantics. This engine expressed in pseudocode is listed as
-Algorithm~\ref{lst:engine}. All the \glspl{Task} are inspected on their waiting
-time. When the waiting time has not passed the delta is subtracted and they are
-pushed to the end of the queue. When the waiting has has surpassed they are
-executed. When a \gls{mTask} wants to queue another \gls{mTask} it can just
-append it to the queue.
-
-\begin{algorithm}[H]
- \KwData{\textbf{queue} queue, \textbf{time} $t, t_p$}
-
- $t\leftarrow\text{now}()$\;
- \Begin{
- \While{true}{
- $t_p\leftarrow t$\;
- $t\leftarrow\text{now}()$\;
- \If{notEmpty$($queue$)$}{
- $task\leftarrow \text{queue.pop}()$\;
- $task$.wait $\leftarrow task$.wait $-(t-t_p)$\;
- \eIf{$task.wait>t_0$}{
- queue.append$(task)$\;
- }{
- run\_task$(task)$\;
- }
- }
- }
- }
- \caption{Engine pseudocode for the \gls{C}- and
- \gls{iTasks}-backend}\label{lst:engine}
-\end{algorithm}
-
\section{Expressions}
Expressions in the \gls{mTask}-\gls{EDSL} are divided into two types, namely
boolean expressions and arithmetic expressions. The class of arithmetic
sds :: ((v t Upd)->In t (Main (v c s))) -> (Main (v c s)) | ...
\end{lstlisting}
+\section{Semantics}
+The \gls{C}-backend of the \gls{mTask}-system has an engine that is generated
+alongside the code for the \glspl{Task}. This engine will execute the
+\glspl{mTask} according to certain rules and semantics.
+\glspl{mTask} do not behave like functions but more like
+\gls{iTasks}-\glspl{Task}. An \gls{mTask} is queued when either his timer runs
+out or when it is started by another \gls{mTask}. When an \gls{mTask} is
+queued it does not block the execution but it will return immediately while
+the actual \gls{Task} will be executed some time in the future.
+
+The \gls{iTasks}-backend simulates the \gls{C}-backend and thus uses the same
+semantics. This engine expressed in pseudocode is listed as
+Algorithm~\ref{lst:engine}. All the \glspl{Task} are inspected on their waiting
+time. When the waiting time has not passed the delta is subtracted and they are
+pushed to the end of the queue. When the waiting has has surpassed they are
+executed. When a \gls{mTask} wants to queue another \gls{mTask} it can just
+append it to the queue.
+
+\begin{algorithm}[H]
+ \KwData{\textbf{queue} queue, \textbf{time} $t, t_p$}
+
+ $t\leftarrow\text{now}()$\;
+ \Begin{
+ \While{true}{
+ $t_p\leftarrow t$\;
+ $t\leftarrow\text{now}()$\;
+ \If{notEmpty$($queue$)$}{
+ $task\leftarrow \text{queue.pop}()$\;
+ $task$.wait $\leftarrow task$.wait $-(t-t_p)$\;
+ \eIf{$task.wait>t_0$}{
+ queue.append$(task)$\;
+ }{
+ run\_task$(task)$\;
+ }
+ }
+ }
+ }
+ \caption{Engine pseudocode for the \gls{C}- and
+ \gls{iTasks}-backend}\label{lst:engine}
+\end{algorithm}
+
+To achieve this in the \gls{EDSL} a \gls{Task} clas are added that work in a
+similar fashion as the \texttt{sds} class. This class is listed in
+Listing~\ref{lst:taskclass}. \glspl{Task} can have an argument and always have
+to specify a delay or waiting time. The type signature of the \CI{mtask} is
+rather arcane and therefore an example is given. The aforementioned Listing
+shows a simple specification containing one task that increments a value
+indefinitely every one seconds.
+
+\begin{lstlisting}[language=Clean,label={lst:taskclass},%
+ caption={The classes for defining tasks}]
+class mtask v a where
+ task :: (((v delay r) a->v MTask Expr)->In (a->v u p) (Main (v t q))) -> Main (v t q) | ...
+
+count = task \count = (\n.count (lit 1000) (n +. One)) In {main = count (lit 1000) Zero}
+\end{lstlisting}
+
\section{Example mTask}
-\todo{Also explain semantics about running tasks}
Some example \glspl{mTask} using almost all of the functionality are shown in
Listing~\ref{lst:exmtask}. The \glspl{mTask} shown in the example do not belong
to a particular view and therefore are of the type \CI{View t r}. The
-\CI{blink} \gls{mTask} show the classic \emph{Arduino} \emph{Hello World!}
-application that blinks a certain LED at each interval. The \CI{thermostat}
-\gls{mTask} will enable a digital pin powering a cooling fan when the analog
+\CI{blink} \gls{mTask} show the classic \gls{Arduino} \emph{Hello World!}
+application that blinks a certain LED every second. The \CI{thermostat}
+expression will enable a digital pin powering a cooling fan when the analog
pin representing a temperature sensor is too high. \CI{thermostat`} shows the
-same program but now using the assignment style \gls{GPIO}.
+same expression but now using the assignment style \gls{GPIO} technique.
\begin{lstlisting}[%
language=Clean,label={lst:exmtask},caption={Some example \glspl{mTask}}]
-blink :: Main (View Int Stmt)
-blink = sds \x=1 In sds \led=LED1 In {main =
- IF (x ==. lit 1) (ledOn led) (ledOff led) :.
- x =. lit 1 -. x
- }
+blink = task \blink=(\x.
+ IF (x ==. lit True) (ledOn led) (ledOff led) :.
+ blink (lit 1000) (Not x)
+ In {main=blink (lit 1000) True}
thermostat :: Main (View () Stmt)
thermostat = {main =
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