-%
-% Basic set operations
-%
-
-% The union of its two arguments.
-\newcommand*{\union}[2]{ {#1}\cup{#2} }
-
-% A three-argument union.
-\newcommand*{\unionthree}[3]{ \union{\union{#1}{#2}}{#3} }
-
-% The intersection of its two arguments.
-\newcommand*{\intersect}[2]{ {#1}\cap{#2} }
-
-% A three-argument intersection.
-\newcommand*{\intersectthree}[3]{ \intersect{\intersect{#1}{#2}}{#3} }
-