Add the \preimage macro.

[mjotex.git] / mjo-arrow.tex

diff --git a/mjo-arrow.tex b/mjo-arrow.tex
index 75b70c9d8b3670d94fb5ed5ca953d20b2464a008..8b44ded1753eb175124ed71fa73ad4e5ec9b35e5 100644 (file)
--- a/mjo-arrow.tex
+++ b/mjo-arrow.tex
@@ -2,6 +2,8 @@
 % Things dealing with arrows in a category. Or functions, basically.
 %
 
+\input{mjo-common}
+
 % The identity operator/arrow on its argument.
 \newcommand*{\identity}[1]{ \operatorname{id}_{{#1}} }
 
@@ -11,3 +13,6 @@
 
 % 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} }