mjo-algebra: add \alg{} for the subalgebra generated by a set.

[mjotex.git] / examples.tex

diff --git a/examples.tex b/examples.tex
index cb7d28a1f41d3a17c02635b370c3cb0fbe36a54f..c00279b16beb44514ae8e80e371d8dc3f8392a35 100644 (file)
--- a/examples.tex
+++ b/examples.tex
@@ -29,7 +29,13 @@
     If $R$ is a \index{commutative ring}, then $\polyring{R}{X,Y,Z}$
     is a multivariate polynomial ring with indeterminates $X$, $Y$,
     and $Z$, and coefficients in $R$. If $R$ is a moreover an integral
-    domain, then its fraction field is $\Frac{R}$.
+    domain, then its fraction field is $\Frac{R}$. If $x,y,z \in R$,
+    then $\ideal{\set{x,y,z}}$ is the ideal generated by
+    $\set{x,y,z}$, which is defined to be the smallest ideal in $R$
+    containing that set. Likewise, if we are in an algebra
+    $\mathcal{A}$ and if $x,y,z \in \mathcal{A}$, then
+    $\alg{\set{x,y,z}}$ is the smallest subalgebra of $\mathcal{A}$
+    containing the set $\set{x,y,z}$.
   \end{section}
 
   \begin{section}{Algorithm}