+
+% 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 function/arrow on its argument.