Documented brand new behavior of sys.ps1 and sys.ps2 (str() is applied
to get the actual prompt).
diff --git a/Doc/lib/libsys.tex b/Doc/lib/libsys.tex
index 1e256af..46c0186 100644
--- a/Doc/lib/libsys.tex
+++ b/Doc/lib/libsys.tex
@@ -167,7 +167,10 @@
Strings specifying the primary and secondary prompt of the
interpreter. These are only defined if the interpreter is in
interactive mode. Their initial values in this case are
- \code{'>>> '} and \code{'... '}.
+ \code{'>>> '} and \code{'... '}. If a non-string object is assigned
+ to either variable, its \code{str()} is re-evaluated each time the
+ interpreter prepares to read a new interactive command; this can be
+ used to implement a dynamic prompt.
\end{datadesc}
\begin{funcdesc}{setcheckinterval}{interval}