>< | ox+/()[] | tip characters |
-.~:= | shaft characters |
When an arrow is interpreted by Xy-pic it is first split into the three components and then each component is looked up in a library of so-called `directionals'. It is possible to add new such directionals using the command
\newdir { directional }{ composite }
|
where directional should be a sequence either of tip
characters or of shaft characters, and composite should be a
list of objects separated with *
just like
the argument to \composite
described in
section 2.2. If arrows of a particular
variant (always one of the letters ^_23
) needs an
alternate definition then another declaration can be given with the
variant inserted between \newdir
and the first {
.
There is one object modifier which is very useful in this
context, in addition to those of section 2.2:
! vector | shift object vector |
(where the possibilities for vector are described in section 2.6). Combined with the direction code this is very powerful, for example,
defines a new tip that makes\newdir{|>}{% !/4.5pt/@{|}*:(1,-.2)@^{>}*:(1,+.2)@_{>}}
typeset\xymatrix{ A \ar @{=|>} [r] & B }
In particular notice how the `relative direction' is used here to rotate some of the composed components.
) is also a
tip character so we can define the directional >
to generate
a `tail-spaced' arrow. Do this such that
typesets\xymatrix{ A \ar @{>->} @< 2pt> [r] \ar @{ >->} @<-2pt> [r] & B }
Finally, when Xy-pic diagrams are used in conjunction with Knuth's computer modern fonts then the declaration
\UseComputerModernTips
|
will change the tips to some that look similar, e.g.,
typesets$\UseComputerModernTips \xymatrix@1{A\ar@{->>|}[r]&B}$