mjo-arrow: add the constant function \const.

diff --git a/examples.tex b/examples.tex
index c1f3df1eb64e416fb00c52f809cdcfc562138324..9e376ccd58757500d96fbf6df2f5395e70b6c39b 100644 (file)
--- a/examples.tex
+++ b/examples.tex
@@ -53,8 +53,9 @@
   \end{section}
 
   \begin{section}{Arrow}
-    The identity operator on $V$ is $\identity{V}$. The composition of
-    $f$ and $g$ is $\compose{f}{g}$. The inverse of $f$ is
+    The constant function that always returns $a$ is $\const{a}$. The
+    identity operator on $V$ is $\identity{V}$. The composition of $f$
+    and $g$ is $\compose{f}{g}$. The inverse of $f$ is
     $\inverse{f}$. If $f$ is a function and $A$ is a subset of its
     domain, then the preimage under $f$ of $A$ is $\preimage{f}{A}$.
   \end{section}

diff --git a/mjo-arrow.tex b/mjo-arrow.tex
index 60530cb71020f3902e3b4c11f9a6498814241f5e..9bf9dc5555515e45f2a98b25d5c89310375d3b03 100644 (file)
--- a/mjo-arrow.tex
+++ b/mjo-arrow.tex
@@ -11,6 +11,18 @@
   \usepackage{amsopn}
 \fi
 
+
+% The constant function that always returns its argument.
+\newcommand*{\const}[1]{\operatorname{const}_{{#1}}}
+
+\ifdefined\newglossaryentry
+  \newglossaryentry{const}{
+    name={\ensuremath{\const{a}}},
+    description={the constant function that always returns $a$},
+    sort=c
+  }
+\fi
+
 % The identity operator/arrow on its argument.
 \newcommand*{\identity}[1]{ \operatorname{id}_{{#1}} }