mention portray_clause/1 and listing/1
@@ -350,7 +350,8 @@ The modules that ship with Scryer&nbsp;Prolog are also called
* [`format`](src/prolog/lib/format.pl)
The nonterminal `format_//2` is used to describe formatted output,
arranging arguments according to a given format&nbsp;string.
- The predicate `format/2` is provided for impure output.
+ The predicates `format/2`, `portray_clause/1` and `listing/1`
+ provide formatted *impure* output.
* [`assoc`](src/prolog/lib/assoc.pl)
providing `empty_assoc/1`, `get_assoc/3`, `put_assoc/4` etc.
to manage elements in AVL&nbsp;trees which ensure
