\usepackage{mathtools}
\fi
+% Create a set from the given elements
+\newcommand*{\set}[1]{\left\lbrace{#1}\right\rbrace}
+
+% A set comprehension, where the ``such that...'' bar is added
+% automatically. The bar was chosen over a colon to avoid ambiguity
+% with the L : V -> V notation. We can't leverage \set here because \middle
+% needs \left and \right present.
+\newcommand*{\setc}[2]{\left\lbrace{#1}\ \middle|\ {#2} \right\rbrace}
+
% The cardinality of a set. The |X| notation conflicts with the
% absolute value, and the meaning of card(X) is clear at once, so we