[project @ 1996-01-08 20:28:12 by partain]

[ghc-hetmet.git] / ghc / docs / add_to_compiler / stg-summary-fig.verb

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+\begin{figure} \fbox{
+$\begin{array}{lrcll}
+%\mbox{Program} & prog & \rightarrow & binds & \\
+%\\
+\mbox{Bindings} & binds & \rightarrow 
+       & bind_1 @;@ \ldots @;@~ bind_n & n \geq 1 \\
+& bind & \rightarrow &  var ~@=@~ vars_f ~@\@ upd~ vars_a ~@->@~expr
+                       & \mbox{Closure} \\
+                       &&&& (vars_f = \freevars{expr} \setminus vars_a) \\
+\\
+\mbox{Update flag} & upd & \rightarrow & @u@ & \mbox{Updatable} \\
+       && | & @n@                              & \mbox{Not updatable} \\
+\\
+\mbox{Expression} & expr 
+       & \rightarrow & @let@~binds~@in@~ expr
+               & \mbox{Local definition} \\
+       && | & @letrec@~binds~@in@~expr
+               & \mbox{Local recursive definition} \\
+       && | & @case@~expr~@of@~alts 
+               & \mbox{Case expression} \\
+       && | & var~vars & \mbox{Application}\\
+       && | & con~vars 
+               & \mbox{Saturated constructor} \\
+       && | & prim~vars 
+               & \mbox{Saturated primitive}   \\
+       && | & literal & \\
+\\
+
+\mbox{Alternatives} & alts & \rightarrow 
+       & calt_1@;@ \ldots @;@~calt_n@; default ->@~ expr 
+               & n \geq 0~\mbox{(Boxed)}       \\
+       && | & lalt_1@;@ \ldots @;@~lalt_n@;@~var ~@->@~ expr 
+               & n \geq 0~\mbox{(Unboxed)}     \\
+\\
+\mbox{Constructor alt} 
+       & calt & \rightarrow & con~vars~@->@~expr &  \\
+\mbox{Literal alt}     
+       & lalt & \rightarrow & literal~@->@~expr &  \\
+\\
+\mbox{Literals} & literal 
+       & \rightarrow & integer                 & \\
+       && | & \ldots & \\
+\\
+\mbox{Primitives} & prim
+       & \rightarrow & @+@ ~|~ @-@ ~|~ @*@ ~|~ @/@ \\
+       && | & \ldots & \\
+\\
+\mbox{Variable lists} & vars & \rightarrow & 
+               @[@var_1@,@ \ldots @,@~var_n@]@                 & n \geq 0 \\
+\\
+\end{array}$
+}
+\caption{Syntax of the STG language}
+\label{fig:stg-syntax}
+\end{figure}