-.SS Functions
-The following functions are provided.
-.PP
-The
-.B sod_subclassp
-function answers whether one class
-.I sub
-is actually a subclass of another class
-.IR super .
-.B sod_subclassp(\c
-.IB sub ,
-.IB super )
-returns nonzero if and only if
-.I sub
-is a subclass of
-.IR super .
-This involves a run-time trawl through the class structures:
-while some effort has been made to make it perform well
-it's still not very fast.
-.PP
-The
-.B sod_convert
-function performs general conversions
-(up-, down-, and cross-casts) on instance pointers.
-Given a class pointer
-.I cls
-and an instance pointer
-.IR obj ,
-.B sod_convert(\c
-.IB cls ,
-.IB obj )
-returns an appropriately converted pointer to
-.I obj
-in the case that
-.I obj
-is an instance of (some subclass of)
-.IR cls ;
-otherwise it returns null.
-This involves a run-time trawl through the class structures:
-while some effort has been made to make it perform well
-it's still not very fast.
-For upcasts (where
-.I cls
-is a superclass of the static type of
-.IR obj )
-the automatically defined conversion macros should be used instead,
-because they're much faster and can't fail.
-When the target class is known statically,
-it's slightly more convenient to use the
-.B SOD_CONVERT
-macro instead.
-.