The \gls{mTask}-\gls{EDSL} is the basis on which the system is built. The
\gls{mTask}-\gls{EDSL} was created by Koopman et al.\ to support several views
such as an \gls{iTasks} simulation and a \gls{C}-code generator. The \gls{EDSL}
-was designed to generate a ready to compile \gls{TOP}-like system for
-microcontrollers such as the Arduino\cite{koopman_type-safe_nodate}%
+was designed to generate a ready-to-compile \gls{TOP}-like system for
+microcontrollers such as the \gls{Arduino}~\cite{koopman_type-safe_nodate}%
\cite{plasmeijer_shallow_2016}.
The \gls{mTask}-\gls{EDSL} is a shallowly embedded class based \gls{EDSL} and
therefore it is very suitable to have a new backend that partly implements the
-given classes. The following sections show the details of the \gls{EDSL}
-that are used in this extension. The parts of the \gls{EDSL} that are not used
-will not be discussed and the details of those parts can be found in the cited
+classes given. The following sections show the details of the \gls{EDSL} that
+are used in this extension. The parts of the \gls{EDSL} that are not used will
+not be discussed and the details of those parts can be found in the cited
literature.
-A view for the \gls{mTask}-\gls{EDSL} is a type of kind \CI{*->*->*} that
-implements some of the classes given. The types do not have to be present as
-fields in the higher kinded view and can, and will most often, solely be
-phantom types. A view is of the form \CI{v t r}. The first variable will be the
-type of the view, the second type variable will be the type of the
-\gls{EDSL}-expression and the third type variable represents the role of the
-expression. Currently the role of the expressions form a hierarchy. The three
-roles and their hierarchy are shown in Listing~\ref{lst:exprhier}. This implies
-that everything is a statement, only a \CI{Upd} and a \CI{Expr} are
-expressions. The \CI{Upd} restriction describes updatable expressions such as
-\gls{GPIO} pins and \gls{SDS}.
+A view for the \gls{mTask}-\gls{EDSL} is a type with kind \CI{*->*->*}%
+\footnote{A type with two free type variables.} that implements some of the
+classes given. The types do not have to be present as fields in the higher
+kinded view and can, and will most often, be exclusively phantom types. A view
+is of the form \CI{v t r}. The first type variable will be the type of the
+view. The second type variable will be the type of the \gls{EDSL}-expression
+and the third type variable represents the role of the expression. Currently
+the role of the expressions form a hierarchy. The three roles and their
+hierarchy are shown in Listing~\ref{lst:exprhier}. This implies that everything
+is a statement, only a \CI{Upd} and a \CI{Expr} are expressions. The \CI{Upd}
+restriction describes updatable expressions such as \gls{GPIO} pins and
+\glspl{SDS}.
\begin{lstlisting}[%
- language=Clean,label={lst:exprhier},caption={Expression role hierarchy}]
+ label={lst:exprhier},caption={Expression role hierarchy}]
:: Upd = Upd
:: Expr = Expr
:: Stmt = Stmt
Expressions in the \gls{mTask}-\gls{EDSL} are divided into two types, namely
boolean expressions and arithmetic expressions. The class of arithmetic
language constructs also contains the function \CI{lit} that lifts a
-host-language value in to the \gls{EDSL} domain. All standard arithmetic
+host-language value into the \gls{EDSL} domain. All standard arithmetic
functions are included in the \gls{EDSL} but are omitted in the example for
brevity. Moreover, the class restrictions are only shown in the first functions
and omitted in subsequent funcitons. Both the boolean expression and arithmetic
expression classes are shown in Listing~\ref{lst:arithbool}.
-\begin{lstlisting}[language=Clean,label={lst:arithbool},
+\begin{lstlisting}[label={lst:arithbool},
caption={Basic classes for expressions}]
class arith v where
lit :: t -> v t Expr
\section{Control flow}
Looping of \glspl{Task} happens because \glspl{Task} are executed after waiting
-a specified amount of time or when they are launched by another task or even
-themselves. Therefore there is no need for loop control flow functionality such
-as \emph{while} or \emph{for} constructions. The main control flow is the
-sequence operator and the \emph{if} statement. Both are shown in
-Listing~\ref{lst:control}. The first class of \emph{If} statements describe the
-regular \emph{if} statement. The expressions given can have any role. The
+a specified amount of time or when they are launched by another \gls{Task} or
+even themselves. Therefore there is no need for loop control flow functionality
+such as \emph{while} or \emph{for} constructions. The main control flow
+operators are the sequence operator and the \emph{if} statement. Both are shown
+in Listing~\ref{lst:control}. The first class of \emph{If} statements describes
+the regular \emph{if} statement. The expressions given can have any role. The
functional dependency on \CI{s} determines the return type of the statement.
-The sequence operator is very straightforward and just ties the two expressions
-together in sequence.
+The listing includes examples of implementations that illustrate this
+dependency.
+
+The sequence operator is very straightforward and its only function is to tie
+the together in sequence.
\begin{lstlisting}[%
- language=Clean,label={lst:control},caption={Control flow operators}]
+ label={lst:control},caption={Control flow operators}]
class If v q r ~s where
If :: (v Bool p) (v t q) (v t r) -> v t s | ...
+instance If Code Stmt Stmt Stmt
+instance If Code e Stmt Stmt
+instance If Code Stmt e Stmt
+instance If Code x y Expr
+
class seq v where
(:.) infixr 0 :: (v t p) (v u q) -> v u Stmt | ...
\end{lstlisting}
\section{Input/Output and class extensions}
-All expressions that have an \CI{Upd} role can be assigned to. Examples of such
-expressions are \glspl{SDS} and \gls{GPIO}. Moreover, class extensions can be
-created for specific peripherals such as user LEDs. The classes facilitating
-this are shown in Listing~\ref{lst:sdsio}. In this way the assignment is the
-same for every assignable entity.
+Values can be assigned to all expressions that have an \CI{Upd} role. Examples
+of such expressions are \glspl{SDS} and \gls{GPIO} pins. Moreover, class
+extensions can be created for specific peripherals such as built-in
+\glspl{LED}. The classes facilitating this are shown in
+Listing~\ref{lst:sdsio}. In this way the assignment is the same for every
+assignable entity.
\begin{lstlisting}[%
- language=Clean,label={lst:sdsio},caption={Input/Output classes}]
+ label={lst:sdsio},caption={Input/Output classes}]
:: DigitalPin = D0 | D1 | D2 | D3 | D4 | D5 |D6 | D7 | D8 | D9 | D10 | D11 | D12 | D13
:: AnalogPin = A0 | A1 | A2 | A3 | A4 | A5
:: UserLED = LED1 | LED2 | LED3
A way of storing data in \glspl{mTask} is using \glspl{SDS}. \glspl{SDS} serve
as variables in the \gls{mTask} and maintain their value across executions.
The classes associated with \glspl{SDS} are listed in
-Listing~\ref{lst:sdsclass}. The \CI{Main} class is introduced to box an
+Listing~\ref{lst:sdsclass}. The \CI{Main} type is introduced to box an
\gls{mTask} and make it recognizable by the type system.
\begin{lstlisting}[%
- language=Clean,label={lst:sdsclass},caption={\glspl{SDS} in \gls{mTask}}]
+ label={lst:sdsclass},caption={\glspl{SDS} in \gls{mTask}}]
:: In a b = In infix 0 a b
:: Main a = {main :: a}
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.
+\gls{iTasks}-\glspl{Task}. An \gls{mTask} is queued when either its timer runs
+out or when it is launched by another \gls{mTask}. When an \gls{mTask} is
+queued it does not block the execution and it will return immediately while
+the actual \gls{Task} will be executed anytime 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.
+time. When the waiting time has not passed; the delta is subtracted and the
+\gls{Task} gets pushed to the end of the queue. When the waiting has surpassed
+they are executed. When an \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} $t, t_p$}
\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
+To achieve this in the \gls{EDSL} a \gls{Task} class is 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
+complex and therefore an example is given. The aforementioned Listing
+shows a simple specification containing one \gls{Task} that increments a value
indefinitely every one seconds.
-\begin{lstlisting}[language=Clean,label={lst:taskclass},%
- caption={The classes for defining tasks}]
+\begin{lstlisting}[label={lst:taskclass},%
+ caption={The classes for defining \glspl{Task}}]
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) | ...
\end{lstlisting}
\section{Example mTask}
-Some example \glspl{mTask} using almost all of the functionality are shown in
+Some example \glspl{mTask} using almost all of their 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 \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 expression but now using the assignment style \gls{GPIO} technique.
+application that blinks a certain \gls{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
+expression but now using the assignment style \gls{GPIO} technique.
\begin{lstlisting}[%
- language=Clean,label={lst:exmtask},caption={Some example \glspl{mTask}}]
+ label={lst:exmtask},caption={Some example \glspl{mTask}}]
blink = task \blink=(\x.
IF (x ==. lit True) (ledOn led) (ledOff led) :.
blink (lit 1000) (Not x)
thermostat :: Main (View () Stmt)
thermostat = {main =
- IF (analogRead A0 >. 50)
+ IF (analogRead A0 >. lit 50)
( digitalWrite D0 (lit True) )
( digitalWrite D0 (lit False) )
}
thermostat` :: Main (View () Stmt)
thermostat` = let
a0 = aIO A0
- d0 = dIO D0 in {main = IF (a0 >. 50) (d0 =. lit True) (d0 =. lit False) }
+ d0 = dIO D0 in {main = IF (a0 >. lit 50) (d0 =. lit True) (d0 =. lit False) }
\end{lstlisting}
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