X-Git-Url: http://gitweb.michael.orlitzky.com/?p=mjotex.git;a=blobdiff_plain;f=mjo-algebra.tex;fp=mjo-algebra.tex;h=c4e70c232ba2ccb8ecbc02a5574052e5cd40a895;hp=fb930279e46e851855845e6e32820e9504ec20a8;hb=914fa9f2b50edcf92abfc98c1341e4c9cd6685f5;hpb=d4abe8806715ebe97343a20ea7a3878307143dc0

diff --git a/mjo-algebra.tex b/mjo-algebra.tex
index fb93027..c4e70c2 100644
--- a/mjo-algebra.tex
+++ b/mjo-algebra.tex
@@ -9,7 +9,17 @@
   \usepackage{amsopn}
 \fi
 
-\input{mjo-common} % for \of, at least
+\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