doc/structures.tex: Mention that the Sod examples are fictitious.

diff --git a/doc/structures.tex b/doc/structures.tex
index 4940ca6..f000af0 100644 (file)
--- a/doc/structures.tex
+++ b/doc/structures.tex
@@ -87,6 +87,12 @@ metaclass, and @|SodClass| is a subclass of @|SodObject|.  Extensions can
 define additional root classes, but this is tricky, and not really to be
 recommended.
 
+The class definitions shown in the synopses are intended to be informative,
+but are fictional and can't really work: these classes are really defined by
+Lisp code in the Sod translator, in order to deal with the circularities
+involved at the top of the class/metaclass graph (see
+\xref{sec:concepts.metaclasses.runtime}).
+
 
 \subsection{The SodObject class} \label{sec:structures.root.sodobject}