ghc/docs/add_to_compiler/stg-summary-fig.verb

   1 \begin{figure} \fbox{
   2 $\begin{array}{lrcll}
   3 %\mbox{Program} & prog & \rightarrow & binds & \\
   4 %\\
   5 \mbox{Bindings} & binds & \rightarrow
   6         & bind_1 @;@ \ldots @;@~ bind_n & n \geq 1 \\
   7 & bind & \rightarrow &  var ~@=@~ vars_f ~@\@ upd~ vars_a ~@->@~expr
   8                         & \mbox{Closure} \\
   9                         &&&& (vars_f = \freevars{expr} \setminus vars_a) \\
  10 \\
  11 \mbox{Update flag} & upd & \rightarrow & @u@ & \mbox{Updatable} \\
  12         && | & @n@                              & \mbox{Not updatable} \\
  13 \\
  14 \mbox{Expression} & expr
  15         & \rightarrow & @let@~binds~@in@~ expr
  16                 & \mbox{Local definition} \\
  17         && | & @letrec@~binds~@in@~expr
  18                 & \mbox{Local recursive definition} \\
  19         && | & @case@~expr~@of@~alts
  20                 & \mbox{Case expression} \\
  21         && | & var~vars & \mbox{Application}\\
  22         && | & con~vars
  23                 & \mbox{Saturated constructor} \\
  24         && | & prim~vars
  25                 & \mbox{Saturated primitive}   \\
  26         && | & literal & \\
  27 \\
  28
  29 \mbox{Alternatives} & alts & \rightarrow
  30         & calt_1@;@ \ldots @;@~calt_n@; default ->@~ expr
  31                 & n \geq 0~\mbox{(Boxed)}       \\
  32         && | & lalt_1@;@ \ldots @;@~lalt_n@;@~var ~@->@~ expr
  33                 & n \geq 0~\mbox{(Unboxed)}     \\
  34 \\
  35 \mbox{Constructor alt}
  36         & calt & \rightarrow & con~vars~@->@~expr &  \\
  37 \mbox{Literal alt}
  38         & lalt & \rightarrow & literal~@->@~expr &  \\
  39 \\
  40 \mbox{Literals} & literal
  41         & \rightarrow & integer                 & \\
  42         && | & \ldots & \\
  43 \\
  44 \mbox{Primitives} & prim
  45         & \rightarrow & @+@ ~|~ @-@ ~|~ @*@ ~|~ @/@ \\
  46         && | & \ldots & \\
  47 \\
  48 \mbox{Variable lists} & vars & \rightarrow &
  49                 @[@var_1@,@ \ldots @,@~var_n@]@                 & n \geq 0 \\
  50 \\
  51 \end{array}$
  52 }
  53 \caption{Syntax of the STG language}
  54 \label{fig:stg-syntax}
  55 \end{figure}