The target []
is the current entry itself.
The author did
Notice how\xymatrix{ {\bullet} \ar@{--}[d]\ar@{=}[dr]\ar@{-}[r] & {\bullet} \ar@{.}[d] \\ {\bullet} & {\bullet} \ar[l] }
{}
since it is an `expandable' entity, i.e., a defined macro.
The author used
\xymatrix{ A \ar[r]^f \ar[dr]_{f;g} & B \ar[d]^g \ar[dr]^{g;h} \\ & C \ar[r]_h & D }
The author used
\xymatrix{ A \ar[d]_f \ar[r]^f & B \ar[dl]|{i_B} \ar[d]^g \\ B \ar[r]_g & C }
The author did
Note that both arrows are curved `above' relative to their direction.\xymatrix{ x \ar@(ul,dl)[]|{id} \ar@/^/[rr]|f && f(x) \ar@/^/[ll]|{f^{-1}} }
The author used the display
In particular notice how the break was specified to happen exactly where the two arrows cross. For an easier but not so general method see exercise 12 last in section 2.7.\xymatrix{ 1 \ar[rr] ^-{1000000x} \ar[dr] _(.2){2000x} |!{[d];[rr]}\hole && 1000000 \\ 1000 \ar[r] _{2x} \ar[urr] _>>{x^2} & 2000 }
The author used the display
\xymatrix{ A \ar[r]^*+[o][F-]{x} & B }
The author used the display
\xymatrix{ A \ar @{/*\composite{{+}*{\times}}/} [rr] ^*+\txt{High\\ label} && B}
The author used the display
\xymatrix{ A \ar @/^/ @{^{<}-_{>}} [r] \ar @/_/ @{{*}{x}{*}} [r] & B }
The author typed
\xymatrix{ A \ar@/^/[r] \ar@/^/@<-1ex>[r] & B }
The size: t+0
always has zero size.
The author typed
The\xymatrix@!{ & \lambda\omega \ar@{-}[rr]\ar@{-}'[d][dd] & & \lambda C \ar@{-}[dd] \\ \lambda2 \ar@{-}[ur]\ar@{-}[rr]\ar@{-}[dd] & & \lambda P2 \ar@{-}[ur]\ar@{-}[dd] \\ & \lambda\ar@{-}\omega \ar@{-}'[r][rr] & & \lambda P\underline\omega \\ \lambda{\to} \ar@{-}[rr]\ar@{-}[ur] & & \lambda P \ar@{-}[ur] }
@!
code added at the top forces rows and columns to be equally spaced as discussed in section 3.3. The gaps could also be made with the !
... crossing notation of exercise 6 last in section 2.1 but the above is shorter.
The author used
\newdir{ >}{{}*!/-5pt/\dir{>}}
The author typed the display
Notice the use of both explicit base and target in the arrow between the labels.\xymatrix{ A \ar[r] ^a="a" & B \ar[r] ^b="b" & C \ar @/^/ "a";"b" }