+% Restrict the first argument (a function) to the second argument (a
+% subset of that functions domain). Abused for polynomials to specify
+% an associated function with a particular domain (also its codomain,
+% in the case of univariate polynomials).
+\newcommand*{\restrict}[2]{{#1}{\restriction}_{#2}}
+\ifdefined\newglossaryentry
+ \newglossaryentry{restriction}{
+ name={\ensuremath{\restrict{f}{X}}},
+ description={the restriction of $f$ to $X$},
+ sort=r
+ }
+\fi
+