X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=mjo-common.tex;h=61ea7c48e7cd8fe0d6ead881d37c5275330b6a0a;hb=5f2d44683ba6cb73b45d572724e827f70641660d;hp=0a9a5d206941c55346153e22bc0b41a8c7cc4510;hpb=58dd2634228390d7a902edf9bf70570e22ebbf4e;p=mjotex.git

diff --git a/mjo-common.tex b/mjo-common.tex
index 0a9a5d2..61ea7c4 100644
--- a/mjo-common.tex
+++ b/mjo-common.tex
@@ -2,6 +2,9 @@
 % Only the most commonly-used macros. Needed by everything else.
 %
 
+% Needed for \mathbb.
+\usepackage{amsfonts}
+
 % Place the argument in matching left/right parntheses.
 \providecommand*{\of}[1]{ \left({#1}\right) }
 
@@ -23,6 +26,9 @@
 % A pair of things.
 \providecommand*{\pair}[2]{ \left({#1},{#2}\right) }
 
+% A triple of things.
+\providecommand*{\triple}[3]{ \left({#1},{#2},{#3}\right) }
+
 % The Cartesian product of two things.
 \providecommand*{\cartprod}[2]{ {#1}\times{#2} }
 
@@ -32,6 +38,9 @@
 % The direct sum of two things.
 \providecommand*{\directsum}[2]{ {#1}\oplus{#2} }
 
+% The direct sum of three things.
+\providecommand*{\directsumthree}[3]{ \directsum{#1}{\directsum{#2}{#3}} }
+
 % The factorial operator.
 \providecommand*{\factorial}[1]{ {#1}! }
 
@@ -68,3 +77,36 @@
 \providecommand*{\Cn}[1][n]{
   \mathbb{C}\if\detokenize{#1}\detokenize{1}{}\else^{#1}\fi
 }
+
+
+%
+% Basic set operations
+%
+
+% The union of its two arguments.
+\providecommand*{\union}[2]{ {#1}\cup{#2} }
+
+% A three-argument union.
+\providecommand*{\unionthree}[3]{ \union{\union{#1}{#2}}{#3} }
+
+% The intersection of its two arguments.
+\providecommand*{\intersect}[2]{ {#1}\cap{#2} }
+
+% A three-argument intersection.
+\providecommand*{\intersectthree}[3]{ \intersect{\intersect{#1}{#2}}{#3} }
+
+% An indexed arbitrary binary operation such as the union or
+% intersection of an infinite number of sets. The first argument is
+% the operator symbol to use, such as \cup for a union. The second
+% argument is the lower index, for example k=1. The third argument is
+% the upper index, such as \infty. Finally the fourth argument should
+% contain the things (e.g. indexed sets) to be operated on.
+\providecommand*{\binopmany}[4]{
+  \mathchoice{ \underset{#2}{\overset{#3}{#1}}{#4} }
+             { {#1}_{#2}^{#3}{#4} }
+             { {#1}_{#2}^{#3}{#4} }
+             { {#1}_{#2}^{#3}{#4} }
+}
+
+\providecommand*{\unionmany}[3]{ \binopmany{\cup}{#1}{#2}{#3} }
+\providecommand*{\intersectmany}[3]{ \binopmany{\cap}{#1}{#2}{#3} }