Document 1.5.2+ aspects of the NotANumber exception. (Note that this
is in the development branch, not the maintenance branch!)
diff --git a/Doc/lib/libfpformat.tex b/Doc/lib/libfpformat.tex
index 94e434c..c67d834 100644
--- a/Doc/lib/libfpformat.tex
+++ b/Doc/lib/libfpformat.tex
@@ -38,8 +38,11 @@
\end{funcdesc}
\begin{excdesc}{NotANumber}
-Exception raised when a string does not look like a number when the
-documentation says it should.
+Exception raised when a string passed to \function{fix()} or
+\function{sci()} as the \var{x} parameter does not look like a number.
+This is a subclass of \exception{ValueError} when the standard
+exceptions are strings. The exception value is the improperly
+formatted string that caused the exception to be raised.
\end{excdesc}
Example: