+\providecommand*{\pair}[2]{ \left({#1},{#2}\right) }
+
+% A triple of things.
+\providecommand*{\triple}[3]{ \left({#1},{#2},{#3}\right) }
+
+% The Cartesian product of two things.
+\providecommand*{\cartprod}[2]{ {#1}\times{#2} }
+
+% The Cartesian product of three things.
+\providecommand*{\cartprodthree}[3]{ \cartprod{{#1}}{\cartprod{{#2}}{{#3}}} }
+
+% The direct sum of two things.
+\providecommand*{\directsum}[2]{ {#1}\oplus{#2} }
+
+% The direct sum of three things.
+\providecommand*{\directsumthree}[3]{ \directsum{#1}{\directsum{#2}{#3}} }
+
+% The factorial operator.
+\providecommand*{\factorial}[1]{ {#1}! }
+
+%
+% Product spaces
+%
+% All of the product spaces (for example, R^n) that follow default to
+% an exponent of ``n'', but that exponent can be changed by providing
+% it as an optional argument. If the exponent given is ``1'', then it
+% will be omitted entirely.
+%
+
+% The natural n-space, N x N x N x ... x N.
+\providecommand*{\Nn}[1][n]{
+ \mathbb{N}\if\detokenize{#1}\detokenize{1}{}\else^{#1}\fi
+}
+
+% The integral n-space, Z x Z x Z x ... x Z.
+\providecommand*{\Zn}[1][n]{
+ \mathbb{Z}\if\detokenize{#1}\detokenize{1}{}\else^{#1}\fi
+}
+
+% The rational n-space, Q x Q x Q x ... x Q.
+\providecommand*{\Qn}[1][n]{
+ \mathbb{Q}\if\detokenize{#1}\detokenize{1}{}\else^{#1}\fi
+}
+
+% The real n-space, R x R x R x ... x R.
+\providecommand*{\Rn}[1][n]{
+ \mathbb{R}\if\detokenize{#1}\detokenize{1}{}\else^{#1}\fi
+}
+
+% The complex n-space, C x C x C x ... x C.
+\providecommand*{\Cn}[1][n]{
+ \mathbb{C}\if\detokenize{#1}\detokenize{1}{}\else^{#1}\fi
+}
+
+% The space of real symmetric n-by-n matrices.
+\providecommand*{\Sn}[1][n]{
+ \mathcal{S}\if\detokenize{#1}\detokenize{1}{}\else^{#1}\fi
+}
+
+% The space of complex Hermitian n-by-n matrices.
+\providecommand*{\Hn}[1][n]{
+ \mathcal{H}\if\detokenize{#1}\detokenize{1}{}\else^{#1}\fi
+}
+
+%
+% Basic set operations
+%
+
+% The union of its two arguments.
+\providecommand*{\union}[2]{ {#1}\cup{#2} }
+
+% A three-argument union.
+\providecommand*{\unionthree}[3]{ \union{\union{#1}{#2}}{#3} }
+
+% The intersection of its two arguments.
+\providecommand*{\intersect}[2]{ {#1}\cap{#2} }
+
+% A three-argument intersection.
+\providecommand*{\intersectthree}[3]{ \intersect{\intersect{#1}{#2}}{#3} }
+
+% An indexed arbitrary binary operation such as the union or
+% intersection of an infinite number of sets. The first argument is
+% the operator symbol to use, such as \cup for a union. The second
+% argument is the lower index, for example k=1. The third argument is
+% the upper index, such as \infty. Finally the fourth argument should
+% contain the things (e.g. indexed sets) to be operated on.
+\providecommand*{\binopmany}[4]{
+ \mathchoice{ \underset{#2}{\overset{#3}{#1}}{#4} }
+ { {#1}_{#2}^{#3}{#4} }
+ { {#1}_{#2}^{#3}{#4} }
+ { {#1}_{#2}^{#3}{#4} }
+}
+
+\providecommand*{\intersectmany}[3]{ \binopmany{\bigcap}{#1}{#2}{#3} }
+\providecommand*{\cartprodmany}[3]{ \binopmany{\bigtimes}{#1}{#2}{#3} }
+\providecommand*{\directsummany}[3]{ \binopmany{\bigoplus}{#1}{#2}{#3} }
+\providecommand*{\unionmany}[3]{ \binopmany{\bigcup}{#1}{#2}{#3} }
+
+
+% The four standard (UNLESS YOU'RE FRENCH) types of intervals along
+% the real line.
+\providecommand*{\intervaloo}[2]{ \left({#1},{#2}\right) } % open-open
+\providecommand*{\intervaloc}[2]{ \left({#1},{#2}\right] } % open-closed
+\providecommand*{\intervalco}[2]{ \left[{#1},{#2}\right) } % closed-open
+\providecommand*{\intervalcc}[2]{ \left[{#1},{#2}\right] } % closed-closed