The list.sort() docs require a function that returns -1, 0 or +1. That's

never been true, and in particular implies cmp() can't be used(!).  Get
closer to the truth.

Doc/lib/libstdtypes.tex

@@ -885,7 +885,7 @@ Notes:
 
 \item[(6)] The \method{sort()} method takes an optional argument
   specifying a comparison function of two arguments (list items) which
-  should return \code{-1}, \code{0} or \code{1} depending on whether
+  should return a negative, zero or positive number depending on whether
   the first argument is considered smaller than, equal to, or larger
   than the second argument.  Note that this slows the sorting process
   down considerably; e.g. to sort a list in reverse order it is much