[Xy-pic] Saving and restoring id-labels.

[Ross Moore]

Hello Mårten,


On 13/10/2004, at 11:54 PM, Mårten Segerkvist wrote:

> Hello!
>
> In the Xy-Pic User's Guide, the answer to exercise 18 on page 14, that 
> is:
>
> \xymatrix{
> A \ar[r] ^a="a" & B \ar[r] ^b="b" & C
>   \ar @/^/ "a";"b" }
>
> results in the following message while parsed LaTeX:
>
> <xymatrix
> ! Use of \next@ doesn't match its definition.
> <argument> \xyeatall@ \everyentry@ A \ar [r] ^a="
>                                                  a"
> l.224   \ar @/^/ "a";"b" }

This looks like trouble with the " character.

What other packages (e.g. Babel) and options are you using ?
Is there anything that changes the \catcode of " ?

If so, then you need to be careful about the order in which
packages are loaded, and to be sure that " has the same
\catcode  when the xy package is loaded, as it will have
when you use \xymatrix and other Xy-pic commands within
the body of your document.


If you don't know what \catcode s are, then send me an
example file that isn't working for you -- complete with
the full preanble that you are using.

Then I'll experiment a bit and show you what needs
to be done in order to get everything working correctly.



>
> ?
> ! Emergency stop.
> <argument> \xyeatall@ \everyentry@ A \ar [r] ^a="
>                                                  a"
> l.224   \ar @/^/ "a";"b" }
>
> As I've got no clue what may cause this, I turn to you with hope of 
> resolving this... If labels aren't possible although the guide claims 
> so I'd be most grateful for any suggestions concerning the 
> possibilities of pointing arrows towards the middle of an arrow in an 
> xymatrix-environment; that is, instead of working around the problem 
> like:
>
> \xymatrix{
> foo\ar`r[rd][rd] & \\
> A\ar[rr] & & B
> }
>
> is it possible to do something like:
>
> \xymatrix{
> foo & \\
> A\ar[r]="a" & B
>   \ar "1,1";"a"
> }

All of this should work, provided Xy-pic knows in advance
what category code " (and all the other non-alphabetic
characters) will have, when trying to build diagrams.

This aspect is in fact discussed in the Xy-pic reference
manual, I believe.


>
> Thanks in advance!
>
> Mårten


Hope this helps,

	Ross


>
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> http://tug.org/mailman/listinfo/xy-pic
>
------------------------------------------------------------------------
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
------------------------------------------------------------------------


------------------------------------------------------------------------
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
------------------------------------------------------------------------