Implemented <, <=, >, >= for sets, giving subset and proper-subset
meanings. I did not add new, e.g., ispropersubset() methods; we're
going nuts on those, and, e.g., there was no "friendly name" for
== either.
diff --git a/Doc/lib/libsets.tex b/Doc/lib/libsets.tex
index 8ce62c8..c5239a4 100644
--- a/Doc/lib/libsets.tex
+++ b/Doc/lib/libsets.tex
@@ -74,9 +74,11 @@
\lineii{\var{x} not in \var{s}}
{test \var{x} for non-membership in \var{s}}
\lineii{\var{s}.issubset(\var{t})}
- {test whether every element in \var{s} is in \var{t}}
+ {test whether every element in \var{s} is in \var{t};
+ \code{\var{s} <= \var{t}} is equivalent}
\lineii{\var{s}.issuperset(\var{t})}
- {test whether every element in \var{t} is in \var{s}}
+ {test whether every element in \var{t} is in \var{s};
+ \code{\var{s} >= \var{t}} is equivalent}
\hline
\lineii{\var{s} | \var{t}}
@@ -99,9 +101,14 @@
{new set with a shallow copy of \var{s}}
\end{tableii}
-In addition to the above operations, both \class{Set} and \class{ImmutableSet}
-support set to set equality comparisons. Two sets are equal if and only if
-every element of each set is contained in the other.
+In addition, both \class{Set} and \class{ImmutableSet}
+support set to set comparisons. Two sets are equal if and only if
+every element of each set is contained in the other (each is a subset
+of the other).
+A set is less than another set if and only if the first set is a proper
+subset of the second set (is a subset, but is not equal).
+A set is greater than another set if and only if the first set is a proper
+superset of the second set (is a superset, but is not equal).
The following table lists operations available in \class{ImmutableSet}
but not found in \class{Set}: