[Xy-pic] \cdot as arrowshaft

[Ross Moore]

Hi Michael,

On 22/01/2007, at 7:36 AM, Michael Barr wrote:

> Is it possible to define a new shaft type that uses \cdot instead  
> of the
> minuscule (and nearly invisible) dots that @{.} gets you?  I have  
> perused
> the manual and it doesn't seem to be mentioned.

You can do it with   \newdir  and  \object (or \composite ).

Study the following example (using french Babel):

\newbox\cdotbox
\setbox\cdotbox=\hbox{\lower1.1ex\hbox{$\cdot$}}
\newdir{d}{\object{\copy\cdotbox}}
$$
\catcode`\! 12 \catcode`\; 12 \catcode`\: 12 \catcode`\? 12
\xy /r.2pc/:
   \POS(0,0)*+!!<0ex,.5ex>{A}="A",\ar@{>}^-{f}(20,0)*+{B}="B"
%  \POS?(.3)*_{g}
   \POS?(.3)*_+!U{g}
\endxy $$
\medskip
$$
\catcode`\! 12 \catcode`\; 12 \catcode`\: 12 \catcode`\? 12
\xy /r.2pc/:
   \POS(0,0)*+!!<0ex,.5ex>{A}="A",{\ar@{{}{d}>}^-{f}(20,0)*+{B}="B"}
   ,"A",\ar@{}"B",
   \POS?(.3)*_+!U{g}
\endxy $$


I've not tested this where the arrow is sloped at some angle.
The trickiest part will be adjusting the size of the contents
of \cdotbox to ensure appropriate spacing of the dots,
for arrows at different angles.



Cheers,

	Ross


>
> Michael Barr

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Ross Moore                                         ross at maths.mq.edu.au
Mathematics Department                             office: E7A-419
Macquarie University                               tel: +61 +2 9850 8955
Sydney, Australia  2109                            fax: +61 +2 9850 8114
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