Comment on extraction settings.

doc/main.tex

@@ -2076,6 +2076,20 @@ library, which can be found in the CompCert tree~\cite{compcert}, in the
 an example if one wishes to use \menhir to generate a formally verified parser
 as part of some other project.
 
+% fp: ce pourrait être bien de documenter les directives nécessaires pour
+% extraire du code efficace. D'après Xavier ce morceau de extraction.v
+% est pertinent:
+\begin{comment}
+(* Int31 *)
+Extract Inductive Int31.digits => "bool" [ "false" "true" ].
+Extract Inductive Int31.int31 => "int" [ "Camlcoq.Int31.constr" ] "Camlcoq.Int31.destr".
+Extract Constant Int31.twice => "Camlcoq.Int31.twice".
+Extract Constant Int31.twice_plus_one => "Camlcoq.Int31.twice_plus_one".
+Extract Constant Int31.compare31 => "Camlcoq.Int31.compare".
+Extract Constant Int31.On => "0".
+Extract Constant Int31.In => "1".
+\end{comment}
+
 % ---------------------------------------------------------------------------------------------------------------------
 
 \section{Comparison with \ocamlyacc}