# [Xy-pic] problem with bending arrows

Thierry Masson thilucmic at yahoo.fr
Fri Mar 9 14:18:40 CET 2007

Hello,

I am trying to understand bending arrows, and the documentations I
find here and there is not clear enough for me! If someone could give
me a very pedestrian introduction, with lot of illustrated exemples,
it would help.
Here is my question.
I have succeed to produce the following diagram:

$\xymatrix at R=15pt at C=25pt{ {} & {A_0} \ar[d] \ar[r] & {B_0} \ar[d] \ar[r] & {C_0} \ar[d] \ar@<-0.5pc>d[dl]+/u0.3pc/ % turn at C1 [ddl]+/l0.3pc/ % turn at B1 [ddll]+/u0.3pc/+/l1pc/ % turn at B2 [dddll]+/l0.2pc/% turn at A2 _-{\partial}% [dddll]+/l0.2pc/+/u0.5pc/ % & {} \\ {} & {A_1} \ar[d] \ar[r] & {B_1} \ar[d] \ar[r] & {C_1} \ar[d] \ar[r] & {0} \\ {0} \ar[r] & {A_2} \ar[d] \ar[r] & {B_2} \ar[d] \ar[r] & {C_2} \ar [d] & {} \\ {} & {A_3} \ar[r] & {B_3} \ar[r] & {C_3}& {} }$

I can't understand why the turns at B1 and A2 don't look like the
turns at C1 and B2. I prefer the C1 and B2 turns. How to modify my
diagram to get the same radius at B1 and A2?
I can't understand why the last straight line from A2 to A3 is not
perfectly vertical... What is wrong about my coding?