Add \zero{R} for the additive identity element in R.

diff --git a/examples.tex b/examples.tex
index 7646b66183ec3ce967677147959b6ef195cb1470..015c5fd67df5aa3e5d4c272c60480694d20ba1ba 100644 (file)
--- a/examples.tex
+++ b/examples.tex
@@ -38,7 +38,8 @@
     containing the set $\set{x,y,z}$.
 
     If $R$ has a multiplicative identity (that is, a unit) element,
-    then that element is denoted by $\unit{R}$.
+    then that element is denoted by $\unit{R}$. Its additive identity
+    element is $\zero{R}$.
   \end{section}
 
   \begin{section}{Algorithm}

diff --git a/mjo-algebra.tex b/mjo-algebra.tex
index 36ad4bd64888c1b2926ff2d454c989e3a561a6aa..25b96d9f8a184edc051ed2867bc8fa9b4b0a269b 100644 (file)
--- a/mjo-algebra.tex
+++ b/mjo-algebra.tex
@@ -12,6 +12,18 @@
 \input{mjo-common} % for \of, and \binopmany
 
 
+% The additive identity element of its argument, which should be
+% an algebraic structure.
+\newcommand*{\zero}[1]{ 0_{{#1}} }
+
+\ifdefined\newglossaryentry
+  \newglossaryentry{zero}{
+    name={\ensuremath{\zero{R}}},
+    description={the additive identity element of $R$},
+    sort=z
+  }
+\fi
+
 % The multiplicative identity element of its argument, which should be
 % an algebraic structure.
 \newcommand*{\unit}[1]{ 1_{{#1}} }