[Xy-pic] pullback symbols

Don MacInnes macinndx@cs.man.ac.uk
Sun, 29 Jul 2001 16:27:30 +0100 (BST)


I'm hoping someone can help by telling me how to draw the little
`right-angle' device often used to show that a certain commuting square is
a pullback/pushout using xypic.

I've looked in the User Guide and also briefly in the Reference Guide, but
can't see it.

Many thanks in advance for your help.

Don MacInnes