architecture/mtasks.tex

   1 \subsection{mTask}
   2 \mTask{}s are written in a shallowly embedded class-based DSL that due to
   3 the nature of it can be easily extended in language and in view. Currently
   4 there is a view for generating \emph{C}-code and a view for simulating
   5 \mTask{}s using \iTasks{}. Currently  the \mTask{} code includes
   6 functionality for running a small task server on the embedded device. These
   7 features will not be used in this project as the microcontroller will serve a
   8 slightly different purpose, namely serve as a task executioner instead of a
   9 server. The bytecode compilation also adds a class that represents all things
  10 compilable in bytecode to make sure all the basic types can be compiled. Both
  11 signatures are shown in Listing~\ref{lst:bytecode}. We only use a subset of the
  12 original \mTask{} definitions because we do not use the functionality for
  13 managing tasks.
  14
  15 \subsection{Classes}
  16 To make the DSL easily extendable with functionality without losing
  17 extendability of views it is defined as a set of classes that can be
  18 implemented by any data type.
  19
  20 Arithmetic operations and boolean operators are defined respectively in the
  21 \CI{arith} and \CI{boolExpr} class. Note that the functions defined by the
  22 class have some restrictions for specific views. This is basically the
  23 translation from Clean basic type to the representation in the data type.
  24
  25 \begin{lstlisting}[language=Clean,label={lst:arith}]
  26 class arith v where
  27         lit :: t -> v t Expr | toCode t & toByteCode t
  28         (+.) infixl 6 :: (v t p) (v t q) -> v t Expr | type, +, zero t & isExpr p & isExpr q
  29         (-.) infixl 6 :: (v t p) (v t q) -> v t Expr | type, -, zero t & isExpr p & isExpr q
  30         (*.) infixl 7 :: (v t p) (v t q) -> v t Expr | type, *, zero, one t & isExpr p & isExpr q
  31         (/.) infixl 7 :: (v t p) (v t q) -> v t Expr | type, / t & isExpr p & isExpr q
  32
  33 class boolExpr v where
  34         (&.) infixr 3 :: (v Bool p) (v Bool q) -> v Bool Expr | isExpr p & isExpr q
  35         (|.) infixr 2 :: (v Bool p) (v Bool q) -> v Bool Expr | isExpr p & isExpr q
  36         Not :: (v Bool p) -> v Bool Expr | isExpr p
  37         (==.) infix 4 :: (v a p) (v a q) -> v Bool Expr | ==, toCode a & isExpr p & isExpr q
  38         (!=.) infix 4 :: (v a p) (v a q) -> v Bool Expr | ==, toCode a & isExpr p & isExpr q
  39         (<.) infix 4 :: (v a p) (v a q) -> v Bool Expr | <, Ord,  toCode a & isExpr p & isExpr q
  40         (>.) infix 4 :: (v a p) (v a q) -> v Bool Expr | <, Ord,  toCode a & isExpr p & isExpr q
  41         (<=.) infix 4 :: (v a p) (v a q) -> v Bool Expr | <, Ord,  toCode a & isExpr p & isExpr q
  42         (>=.) infix 4 :: (v a p) (v a q) -> v Bool Expr | <, Ord,  toCode a & isExpr p & isExpr q
  43 \end{lstlisting}
  44
  45
  46 In the future a state will probably need to be added to the \CI{Bytecode}
  47 type to keep track of some information during bytecode compilation.
  48
  49 \begin{lstlisting}[language=Clean,label={lst:bytecode}]
  50 :: BC
  51         = BCNop
  52         | BCPush Int
  53         | BCPop
  54         ...
  55
  56 :: ByteCode a p = BC [BC]
  57 class toByteCode a :: a -> [Char]
  58 \end{lstlisting}