Labels

??=[basics.labels] You can put labels on arrows. Labels are conceptualized as sub- and superscripts on arrows such that they are placed in the usual positions (as `limits'), , |^| reads `above' and |_| below on an arrow pointing "right" but the positions depend only on the direction of the arrow. For example,
\begin{code} \diagram X \rto^a_b & Y & Z \lto^A_B \enddiagram \end{code}
will set

$\displaystyle \docode$

Labels that do not consist of a single letter, digit, or control sequence, should be enclosed in ||...||.

The placement of the labels only depends on the direction of the arrow: it is placed perpendicular to the center of the arrow (measured from the centers of the objects at the ends). More details concerning labels are given in section ??[arrows.labels].


\begin{exercise} \begin{code} \begin{displaymath}\diagram A \rto^f \drto_{f;g} ... ...\answercode \answertext{The author used the display \displaycode} \end{exercise}