deliverables/report/intro.tex

   1 \section{Introduction}
   2 \subsection{\SPLC}
   3 \SPLC{} is a program written in the purely functional lazy programming language
   4 Clean\footnote{\url{http://clean.cs.ru.nl/Clean}}. \SPLC{} has a standardized
   5 UNIX like command line interface and functions as a filter in a way that it
   6 processes standard input to standard output. Default command line argument such
   7 as \texttt{--version} and \texttt{--help} provide the expected output. To
   8 illustrate all the command line interface options the output of \texttt{spl
   9 --help} is given in Listing~\ref{lst:splchelp}.
  10
  11 \begin{lstlisting}[
  12         label={lst:splchelp},
  13         caption={Output of \texttt{./spl -h}}]
  14 Usage: spl [OPTION] [FILE]
  15
  16 Options:
  17   --help             Show this help
  18   --version          Show the version
  19   --[no-]lex         Lexer output(default: disabled)
  20   --[no-]parse       Parser output(default: disabled)
  21   --[no-]sem         Semantic analysis output(default: disabled)
  22   --[no-]code        Code generation output(default: enabled)
  23 \end{lstlisting}
  24
  25 \subsection{Outline}
  26 \SPLC{} has several phases that each can produce their own output. Via command
  27 line flags the user can enable or disable the printing of the output of
  28 specific phases. The output for the code generation is enabled by default and
  29 the output for the other phases are disabled by default.
  30
  31 The first and second step are lexing and parsing, which are both explained in
  32 Section~\ref{sec:pars}. When one enables only the parsing the program will show
  33 the pretty printed parsed source which is valid \SPL{} code. A simple selftest
  34 can thus be done by feeding the pretty printed output back into \SPLC{}. This
  35 is show in Listing~\ref{lst:splcex}.
  36
  37 The third phase is the semantic analysis phase. In this phase the types are
  38 inferred where necessary and they are checked. There are also some trivial
  39 sanity checks executed to make sure the program is a valid one. When one
  40 enables the printing of the third phase you are shown the pretty printed source
  41 code with all types inferred and the internal dictionary used for typechecking.
  42 This phase is elaborated upon in Section~\ref{sec:sem}.
  43
  44 The last and fourth phase is the code generation phase. \SPLC{} generates
  45 \SSM\footnote{\url{http://www.staff.science.uu.nl/~dijks106/SSM/}}
  46 assembly. \SSM{} assembly is a educational assembly language designed for
  47 compiler construction courses and provides the programmer with handy tools such
  48 as an emulator, breakpoints and a couple of higher level assembly instructions.
  49 Details on code generation is explained in Section~\ref{sec:gen}. Since \SPLC{}
  50 acts as a filter and the \SSM{} emulator does too one can chain the commands
  51 together with standard pipes as shown in Listing~\ref{lst:splcex}.
  52
  53 In the Section~\ref{sec:ext} it is explained what extra features \SPLC{}
  54 contains. Some syntactic sugars have been added in combination with support for
  55 higher order functions.
  56
  57 \begin{lstlisting}[
  58         label={lst:splcex},
  59         caption={Example \SPLC{} run},
  60         language=sh]
  61 # Run a program
  62 spl input.spl | java -jar ssm.jar --stdin --cli
  63 # Selftest parser
  64 diff -q \
  65         <(spl --parse --no-code input.spl) \
  66         <(spl --parse --no-code input.spl | spl --parse --no-code)
  67 \end{lstlisting}