Xy-pic User's Guide

2.1 Explicit label positioning

The label commands explained in section 1.4 place the label text near the point along the arrow halfway between the centers of the base and target entries. This, however, may be changed by inserting a place between the ^, _, or |, and the actual label (in fact - is a place). In general you may insert the following:

• < will place the label at the point where the actual arrow begins, i.e., "appears from under" the base, so $\xymatrix@1{A\ar[r]^<{+}&B}$ will typeset .
• Similarly, > will place the label at the point where the actual arrow ends, i.e., "disappears below" the target, so $\xymatrix@1{A\ar[r]^>{+}&B}$ will typeset .
• << and >> will place the following label at a point just a bit further from the beginning and end of the arrow, so $\xymatrix@1{A\ar[r]^>>{+}&B}$ will typeset . Using more <s or >s will move the label further in.
• A factor in ()s: indicates that the label should be "tied" to the point a of the way from the center of the base entry (called (0)) to the center of the target (called (1)) instead of in the middle, so $\xymatrix@1{A\ar[r]^(.3){+}&B}$ will typeset .
• A factor can be given after some < or >s, in which case the place is computed as if the base was specified by the <s and target specified by the >s. Hence $\xymatrix@1{A\ar[r]^<(0){+}&B}$ will typeset .
• Finally, there is a simple way to denote the place on an arrow where it intersects with a straight line between two points: the place !{;} places the label relative to the point on the arrow where the line from the target to the target crosses it. BUG: Only works for straight arrows at present.

As usual more possibilities can be found in the reference manual [8, fig. 2,].

 

Exercise 6.

Typeset

Answer.

 

Xy-pic User's Guide