+@c @item %source_extension
+@c Specify the extension of the parser output file.
+@c
+@c For example, a grammar file named @file{foo.yy} and containing a
+@c @code{%source_extension .cpp} directive will produce a parser file
+@c named @file{foo.tab.cpp}
+@c
+@c @item %header_extension
+@c Specify the extension of the parser header file generated when
+@c @code{%define} or @samp{-d} are used.
+@c
+@c For example, a garmmar file named @file{foo.ypp} and containing a
+@c @code{%header_extension .hh} directive will produce a header file
+@c named @file{foo.tab.hh}
+