The following predicates all have their standard Edinburgh definitions:
-->
->
/
//
<<
=
=
=<
>>
?-
@<
@>
@>=
\,
\.
\:-
\:=
\;
\\
\\
\\+
\\/
\\=
\\==
^
current-op
display
get
get0
is
name
nl
put
see
seeing
seen
skip
tell
telling
told
ttynl
ttyput
write
writeq
|is|