All arrows are obtained through the \ar
command which takes
many options of which we will describe a few here and some more in
section 2. In its simplest form an arrow is entered as
\ar[
hop]
where hop is a sequence of
single letters: u
for up, d
for down, l
for left,
and r
for right, e.g., the arrow \ar[ur]
reads `typeset an
arrow from the current entry to that one up and one right'.
[]
refer to?
The relative coordinates specified in this way are purely logical, e.g., if the diagram contains very wide entries then the arrows will be nearly horizontal. The constructed arrows are aligned along the line between the centers of the base and target entries; they will not automatically disappear under entries that they cross (we discuss how this is achieved in section 2.7).
The arrow style kan be changed by writing the command as
\ar@
style[
hop]
. This will be described in
more detail in section 2.3; here we just list the most
common @
styles (most obvious variations also work):