doc/concepts.tex: Fix missing superclass in a code example.

diff --git a/doc/concepts.tex b/doc/concepts.tex
index 759153b5bc646007417372a3546577914c3ae667..f7283e4a6069d781f5eb35af81d79257a375fd55 100644 (file)
--- a/doc/concepts.tex
+++ b/doc/concepts.tex
@@ -856,7 +856,7 @@ This simple protocol can be used, for example, to implement a reference
 counting system, as follows.
 \begin{prog}
   [nick = ref]                                                  \\
 counting system, as follows.
 \begin{prog}
   [nick = ref]                                                  \\

-  class ReferenceCountedObject \{                               \\ \ind
+  class ReferenceCountedObject: SodObject \{                    \\ \ind

     unsigned nref = 1;                                          \\-
     void inc() \{ me@->ref.nref++; \}                           \\-
     [role = around]                                             \\
     unsigned nref = 1;                                          \\-
     void inc() \{ me@->ref.nref++; \}                           \\-
     [role = around]                                             \\