[Xy-pic] Questionable behaviour of the arrow extension
Johann Bauer
jbauer-news at web.de
Wed Aug 23 22:07:30 CEST 2006
Hello,
the arrow extension behaves strangely in two instances that came up when
I drew some mathematical diagrams. I would be grateful if someone could
help me with these problems.
1) xypic outputs for each arrow (\ar) obviously three paths: two at both
ends of the stem of (nearly) length zero and the proper one for the
stem. I discovered this when I increased the linewidth for a certain
diagram. The effect becomes obvious in the following example. Note that
this bug (?) occurs independent of the "line" extension - I just used
this to demonstrate the effect.
\documentclass{minimal}
\usepackage[arrow,line,dvips]{xy}
\begin{document}
\xy <3pc,0pc>:<0pc,2pc>::
\ar@[|<30pt>]@[projcap]@{-} (10,10)
\endxy
\end{document}
Without the line extension, the additional paths can be seen in the
postscript output (generated by dvips):
%%Page: 1 1
TeXDict begin 1 0 bop 0 26567 a
SDict begin {pu 2 lc 30.0 lw}xyg end
0 26567 a -2672 x @beginspecial
@setspecial
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
{0.0 0.14063 l}xy % Unwanted!
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@endspecial 0 26567 a
SDict begin { pp}xyf end
0 26567 a 0 26567
a
SDict begin {pu 2 lc 30.0 lw}xyg end
0 26567 a 39851 0 a @beginspecial @setspecial
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
{360.0 216.0 l}xy % This is the proper arrow stem
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@endspecial
0 26567 a
SDict begin { pp}xyf end
0 26567 a 0 26567 a
SDict begin {pu 2 lc 30.0 lw}xyg end
0 26567 a 39851 0 a @beginspecial
@setspecial
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
{0.0 0.14063 l}xy % Unwanted!
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@endspecial 0 26567 a
SDict begin { pp}xyf end
0 26567 a eop end
%%Trailer
How can I get rid of these (nearly) zero paths? They create ugly
artefacts in some of the diagrams I wrote.
2) Another strange output comes from this example:
\documentclass{minimal}
\usepackage[arrow]{xy}
\begin{document}
\xy
(0,0), {\ar@{=} (10,0)},
(20,0), {\PATH ~={**\dir{.}} '(30,0) (30,10)},
(0,20), {\ar@{=} (00,30)},
(20,20), {\PATH ~={**\dir{.}} '(30,20) (30,30)},
\endxy
\end{document}
Here, the arrow command causes the succeeding path to be drawn twice:
once with its own style (here: dotted) and once with the arrow style
(here: double line). To avoid this, I can of course move all the arrow
commands to the end of the diagram. But is this a bug in xypic or did I
just not understand the syntax rules? What would then be the correct syntax?
Thanks in advance for any help!
Johann Bauer
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