mtask.io.tex

   1 Values can be assigned to all expressions that have an \CI{Upd} role. Examples
   2 of such expressions are \glspl{SDS} and \gls{GPIO} pins. Moreover, class
   3 extensions can be created for specific peripherals such as built-in
   4 \glspl{LED}. The classes facilitating this are shown in
   5 Listing~\ref{lst:sdsio}. In this way the assignment is the same for every
   6 assignable entity.
   7
   8 \begin{lstlisting}[%
   9         label={lst:sdsio},caption={Input/Output classes}]
  10 :: DigitalPin = D0 | D1 | D2 | D3 | D4 | D5 |D6 | D7 | D8 | D9 | D10 | D11 | D12 | D13
  11 :: AnalogPin  = A0 | A1 | A2 | A3 | A4 | A5
  12 :: UserLED = LED1 | LED2 | LED3
  13
  14 class dIO v where dIO :: DigitalPin -> v Bool Upd
  15 class aIO v where aIO :: AnalogPin -> v Int Upd
  16 class analogRead v where
  17   analogRead :: AnalogPin -> v Int Expr
  18   analogWrite :: AnalogPin (v Int p) -> v Int Expr
  19 class digitalRead v where
  20   digitalRead :: DigitalPin -> v Bin Expr
  21   digitalWrite :: DigitalPin (v Bool p) -> v Int Expr
  22
  23 :: UserLED = LED1 | LED2 | LED3
  24 class userLed v where
  25   ledOn  :: (v UserLED q) -> (v () Stmt)
  26   ledOff :: (v UserLED q) -> (v () Stmt)
  27
  28 class assign v where
  29   (=.) infixr 2 :: (v t Upd) (v t p) -> v t Expr | ...
  30 \end{lstlisting}
  31
  32 One way of storing data in \gls{mTask}-\glspl{Task} is using \glspl{SDS}.
  33 \glspl{SDS} serve as variables in \gls{mTask} and maintain their value across
  34 executions.  \glspl{SDS} can be used by multiple \glspl{Task} and can be used
  35 to share data. The classes associated with \glspl{SDS} are listed in
  36 Listing~\ref{lst:sdsclass}. The \CI{Main} type is introduced to box an
  37 \gls{mTask} and make it recognizable by the type system by separating programs
  38 and decorations such as \glspl{SDS}.
  39
  40 \begin{lstlisting}[%
  41         label={lst:sdsclass},caption={\glspl{SDS} in \gls{mTask}}]
  42 :: In a b = In infix 0 a b
  43 :: Main a = {main :: a}
  44
  45 class sds v where
  46   sds :: ((v t Upd)->In t (Main (v c s))) -> (Main (v c s)) | ...
  47 \end{lstlisting}
  48
  49 In the \emph{Arduino} ecosystem, shields are available to plug into the
  50 microcontroller and add functionality. These shields range from Bluetooth,
  51 WiFi, Ethernet, LoRa, LCD screens and much more. Often the functionality
  52 available in these shields is housed in a \gls{C++} class. This functionality
  53 is ported using little work to \gls{mTask} by just creating a corresponding
  54 class with the same functions. As an example, Listing~\ref{lst:lcd} shows parts
  55 of the \gls{LCD} class as an \gls{mTask} class functions and as
  56 Listing~\ref{lst:lcdc} shown the corresponding \emph{Arduino} class functions.
  57
  58 \begin{lstlisting}[label={lst:lcd},%
  59         caption={Adding the \gls{LCD} to the \gls{mTask} language}]
  60 :: LCD = ...
  61
  62 class lcd v where
  63   begin          :: (v LCD Expr) (v Int p) (v Int q) -> v () Expr
  64   ...
  65   scrollLeft     :: (v LCD Expr) -> v () Expr
  66   scrollRight    :: (v LCD Expr) -> v () Expr
  67   ...
  68 \end{lstlisting}
  69
  70 \begin{lstlisting}[language=C++,label={lst:lcdc},%
  71         caption={Functions from the \gls{Arduino} \gls{LCD} library}]
  72 class LiquidCrystal {
  73 public:
  74   void begin(uint8_t cols, uint8_t rows);
  75   ...
  76   void scrollDisplayLeft();
  77   void scrollDisplayRight();
  78   ...
  79 }
  80 \end{lstlisting}