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

[Mårten Segerkvist]

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" }

?
! 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"
}

Thanks in advance!

Mårten