t.s | merge t with simple s |
{t} | make t simple |
The first will enlarge t to also `cover' the `simple' s
(simple means that it cannot have changes etc. attached unless
encapsulated in {}s). Here is an example where we merge and
frame:
\xymatrix{ 1,1 & 1,2 & 1,3 & 1,4 & 1,5 \\
2,1 & 2,2 & 2,3 & 2,4 & 2,5
\save "1,2"."2,4"*[F.]\frm{}
\ar"1,1" \ar"2,1" \ar"1,5" \ar"2,5"
\restore }
will typeset

As you can see, the center of the merged object is the same as the
one of the target before the `.'.
Finally a more advanced example where we create two merged objects
with center in their `real' center, name them and then connect
to them. It also shows how macros can be used inside diagrams: they
should always expand to `commands' like \ar..., etc.:

can be typeset by
\def\g#1{\save.[dr]!C="g#1"*[F]\frm{}\restore}%
\xymatrix{
\g1 A\ar[r]&B\ar[d]&\g2 A'\ar[r]&B'\ar[d]\\
C\ar[u]&D\ar[l]& C'\ar[u]&D'\ar[l]
\ar @{.>} "g1" ;"1,4"
\ar @{-->} "2,1";"g2" }
Then we can make arrows from/to the two frames by using the two new
targets "g1" and "g2" as shown.