Contents of Explicit positioning of labels

Explicit positioning of labels

??=[arrows.labels] The label commands explained in section ??[basics.labels] place the label text near the center of the arrow. This, however, may be changed by inserting a "??w![place]" between the ??c![^], ??c![_], or ??c![|], and the actual label. In general you may insert the following:

??c![<] will place the label at the point where the actual arrow begins, , `appears from under' the base, so
$\begin{code} \diagram A \rto^<{+} &B \enddiagram \end{code}$
will typeset .
Similarly, ??c![>] will place the label at the point where the actual arrow ends, , `disappears below' the target, so
$\begin{code} \diagram A \rto^>{+} &B \enddiagram \end{code}$
will typeset .
??c![«] and ??c![»] will place the following label at a point just a bit³ further from the beginning and end of the arrow, so
$\begin{code} \diagram A \rto^>>{+} &B \enddiagram \end{code}$
will typeset . Using more |<|s will move the label further in.
More |<|s and |>|s may be given to make this distance larger:
$\begin{code} \diagram A \rto^>>>{+} &B \enddiagram \end{code}$
will typeset .
A factor in ??c![()]s: |(| a|)| indicates that the label should be `tied' to the point a of the way from the center of the base entry (called ??c![(0)]) to the center of the target (called ??c![(1)]) instead of in the middle, so
$\begin{code} \diagram A \rto^(.3){+} &B \enddiagram \end{code}$
will typeset .
A factor can be given "after" some |<| or |>|s: in that case the place is computed as if the base was the place specified by the |<|s and the target the place specified by the |>|s:
$\begin{code} \diagram A \rto^<(0){+} &B \enddiagram \end{code}$
will typeset .
Finally, a ??c![-] means the same as |<>(.5)|, , place at the "middle of the arrow" rather than the middle between the base and target, so
$\begin{code} \diagram A\times B\times C\times D \rto^-{+} &B \enddiagram \end{code}$
was typeset by It becomes A×B×C×D ^+ &B without |-| .

$\begin{exercise} \begin{code} \diagram A \dto ^>>\ast ^b \drto ^>>\ast ^c \rto... ...\answercode \answertext{The author used the display \displaycode} \end{exercise}$