X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=mjo-arrow.tex;h=60530cb71020f3902e3b4c11f9a6498814241f5e;hb=71b85fe2012cdf733f6e72137038d7d9960ddf08;hp=3ae2daac179659b681c3ab9d14990250cf80bb31;hpb=5c1a943a2ae3886693c0361084239aef9da3551c;p=mjotex.git

diff --git a/mjo-arrow.tex b/mjo-arrow.tex
index 3ae2daa..60530cb 100644
--- a/mjo-arrow.tex
+++ b/mjo-arrow.tex
@@ -1,10 +1,28 @@
 %
 % Things dealing with arrows in a category. Or functions, basically.
 %
+\ifx\havemjoarrow\undefined
+\def\havemjoarrow{1}
+
+
+\input{mjo-common} % for \of, at least.
+
+\ifx\operatorname\undefined
+  \usepackage{amsopn}
+\fi
 
 % The identity operator/arrow on its argument.
 \newcommand*{\identity}[1]{ \operatorname{id}_{{#1}} }
 
 % The composition of two arrows/functions. For example, the
 % composition of g with f is \compose{g}{f}\of{x} === g\of{f\of{x}}.
-\newcommand*{\compose}[2]{ {#1} \circ {#2} }
+\newcommand*{\compose}[2]{ {#1}\circ{#2} }
+
+% The inverse of an arrow, function, or whatever.
+\newcommand*{\inverse}[1]{ #1^{-1} }
+
+% The preimage of the second argument (a set) under the first (a function).
+\newcommand*{\preimage}[2]{ #1^{-1}\of{#2} }
+
+
+\fi