methods.top.tex

   1 \section{\acrlong{TOP}}
   2 \subsection{\gls{iTasks}}
   3 \gls{TOP} is a recent programming paradigm implemented as
   4 \gls{iTasks}\cite{achten_introduction_2015} in the pure lazy functional
   5 language \gls{Clean}\cite{brus_cleanlanguage_1987}. \gls{iTasks} is a
   6 \gls{EDSL} to model workflow tasks in the broadest sense. A \CI{Task} is just
   7 a function that, given some state, returns the observable \CI{TaskValue}. The
   8 \CI{TaskValue} of a \CI{Task} can have different states. Not all state
   9 transitions are possible as shown in Figure~\ref{fig:taskvalue}. Once a value
  10 is stable it can never become unstable again. Stability is often reached
  11 by pressing a confirmation button. \glspl{Task} yielding a constant value are
  12 immediately stable.
  13
  14 A simple \gls{iTasks} example illustrating the route to stability of a
  15 \gls{Task} in which the user has to enter a full name is shown in
  16 Listing~\ref{lst:taskex}. The code is accompanied by screenshots showing the
  17 user interface in Figure~\ref{fig:taskex1},~\ref{fig:taskex2}
  18 and~\ref{fig:taskex3}. The \CI{TaskValue} of the \gls{Task} is in the first
  19 image in the \CI{NoValue} state, the second image does not have all the fields
  20 filled in and therefore the \CI{TaskValue} remains \CI{Unstable}. In the third
  21 image all fields are entered and the \CI{TaskValue} transitions to the
  22 \CI{Unstable} state. When the user presses \emph{Continue} the value becomes
  23 \CI{Stable} and can not be changed any further.
  24
  25 \begin{figure}[H]
  26         \centering
  27         \includegraphics[width=.5\linewidth]{fig-taskvalue}
  28         \caption{The states of a \CI{TaskValue}}\label{fig:taskvalue}
  29 \end{figure}
  30
  31 \begin{lstlisting}[language=Clean,label={lst:taskex},%
  32         caption={An example \gls{Task} for entering a name}]
  33 :: Name = { firstname :: String
  34           , lastname  :: String
  35           }
  36
  37 derive class iTask Name
  38
  39 enterInformation :: String [EnterOption m] -> (Task m) | iTask m
  40
  41 enterName :: Task Name
  42 enterName = enterInformation "Enter your name" []
  43 \end{lstlisting}
  44
  45 \begin{figure}[H]
  46         \begin{subfigure}{.25\textwidth}
  47                 \centering
  48                 \includegraphics[width=.9\linewidth]{taskex1}
  49                 \caption{Initial interface}\label{fig:taskex1}
  50         \end{subfigure}
  51         \begin{subfigure}{.25\textwidth}
  52                 \centering
  53                 \includegraphics[width=.9\linewidth]{taskex2}
  54                 \caption{Incomplete entrance}\label{fig:taskex2}
  55         \end{subfigure}
  56         \begin{subfigure}{.25\textwidth}
  57                 \centering
  58                 \includegraphics[width=.9\linewidth]{taskex3}
  59                 \caption{Complete entry}\label{fig:taskex3}
  60         \end{subfigure}
  61         \caption{Example of a generated user interface}
  62 \end{figure}
  63
  64 For a type to be suitable it must have instances for a collection of generic
  65 functions that are captured in the class \CI{iTask}. Basic types have
  66 specialization instances for these functions and show an according interface.
  67 Generated interfaces can be modified with decoration operators.
  68
  69 \subsection{Combinators}
  70 \todo{Stukje over combinators, in ieder geval bind en paralel}