fix up whitespace in prompt strings
diff --git a/Doc/lib/libsys.tex b/Doc/lib/libsys.tex
index 8a23fbc..686e50e 100644
--- a/Doc/lib/libsys.tex
+++ b/Doc/lib/libsys.tex
@@ -410,7 +410,7 @@
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{'... '}. If a non-string object is
+ \code{'>>>~'} and \code{'...~'}. If a non-string object is
assigned to either variable, its \function{str()} is re-evaluated
each time the interpreter prepares to read a new interactive
command; this can be used to implement a dynamic prompt.