[Xy-pic] Strange error when typesetting a diagram

[Ross Moore]

On 11/12/2004, at 1:37 AM, HomXY at gmx.de wrote:

> Hello,
>
> I'am trying to typeset the following:
>
> $$\xymatrix{&\pi_1(S) \ar[rd]^{\rho}\\
> \pi_1(S\cap S'*)\ar@/^/[rr]^{\rho\circ i_{S\cap
> S'*}}\ar@/_/[rr]_{\rho'\circ i_{S\cap S'*}}
> \ar@{->>}[ru]^{i_{S\cap S'*}}\ar@{->>}[rd]_{i_{S\cap
> S'}}&&{Gl_r(C)} \ar@(ur, dr)[]^\kappa\\
> &\pi_1(S')\ar[ru]_{\rho '}}$$
>
> The arrow
>
> \ar@(ur, dr)[]^\kappa

This is a self-arrow, on the object   Gl_r(C) .
(BTW, better is  \mathrm{Gl}_r(\mathbb{C})
  with  \usepackage{amsmath}  for the \mathbb to work)

That is a large object, so most of the arrow will be
obscured --- perhaps all, so Xy-pic cannot determine
where to start drawing.

You need to move the base-point for the arrow
towards the right-hand end on the object.
Do this as follows:

\mathrm{Gl}_r(\mathbb{C})\POS!R(.7),\ar@(ur,dr)^\kappa

Try the effect of changing that number (.7) to values
greater, up to 1, or lower until the error occurs.



Also, this is the kind of diagram that looks better
with the more open, CM, style of arrowhead.

viz.

\usepackage[all,tips]{xy}


$$\SelectTips{cm}{10}
\xymatrix{%
&\pi_1(S) \ar[rd]^{\rho}\\
\pi_1(S\cap S'*)\ar@/^/[rr]^{\rho\circ i_{S\cap S'*}}
\ar@/_/[rr]_{\rho'\circ i_{S\cap S'*}}
\ar@{->>}[ru]^{i_{S\cap S'*}}\ar@{->>}[rd]_{i_{S\cap S'}}
&& \mathrm{Gl}_r(\mathbb{C}) {\POS!R(.7),\ar@(ur, dr)^\kappa}\\
&\pi_1(S')\ar[ru]_{\rho '}}
$$


>
> produces an error message. Can you help me?


The above should help,


Regards,

	Ross


>
> Runaway argument?
> @@\expandafter \edef \xysplineedges@ {\splineedges@ }\global \let \ETC.
> ! Paragraph ended before \testsplineedges@ was complete.
> <to be read again>
>                    \par
>
> Thanks
>
> Sönke
>
> -- 
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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                                  fax: +61 +2 9850 8114
------------------------------------------------------------------------