X-Git-Url: http://gitweb.michael.orlitzky.com/?p=mjotex.git;a=blobdiff_plain;f=mjo-algebra.tex;h=c4e70c232ba2ccb8ecbc02a5574052e5cd40a895;hp=59d94874e9a13e38a83bb5274e3c5666fa9e17d3;hb=f9205a3b883c08499edfdd3f9d1a6170a6fc6755;hpb=85d35b1401a30045cb5b3bca5e8faea5a3248bb3

diff --git a/mjo-algebra.tex b/mjo-algebra.tex
index 59d9487..c4e70c2 100644
--- a/mjo-algebra.tex
+++ b/mjo-algebra.tex
@@ -9,7 +9,17 @@
   \usepackage{amsopn}
 \fi
 
-\input{mjo-common}
+\input{mjo-common} % for \of, and \binopmany
+
+
+% The direct sum of two things.
+\newcommand*{\directsum}[2]{ {#1}\oplus{#2} }
+
+% The direct sum of three things.
+\newcommand*{\directsumthree}[3]{ \directsum{#1}{\directsum{#2}{#3}} }
+
+% The (indexed) direct sum of many things.
+\newcommand*{\directsummany}[3]{ \binopmany{\bigoplus}{#1}{#2}{#3} }
 
 
 % The (sub)algebra generated by its argument, a subset of some ambient