How do I make the arrow -->-- using xymatrix?

Question

I do not know any TikZ so I cannot use this post, which otherwise is precisely what I am looking for. So how do I make such a square? The best I could come up with was

\ar@{-}[r]^{\delta}|-{>}

but it doesn't look good and does not work on vertical lines/arrows.

Now, having done this square my guess would be that the corners would be empty, that is, the edges would not meet each other. How do I fix that problem?

Answer 1

You want an arrowhead in the middle of the arrow? Use the ‘break’ via |-*=0@{>}. This drops the directional tip, taking up no space. It should work whatever the direction of the arrow.

Hope this helps,

Ross

BTW, the list Xy-pic@tug.org is the best point of contact for Xy-pic related questions.