[Xy-pic] A newbbie Question

[Mansour Al-Aqeel]

Hi every body: 
I'm trying to figure out how to style an arrow. For some reason, I'm
getting an error when ever I use @.
That's the latex code i ws trying to veiw.

\entrymodifiers={++[o][F-]}
\xymatrix @-1pc { A\ar@{=>}[d] \\ B }

and after I deleted  @-1pc, it became 
\xymatrix  { A\ar@{=>}[d] \\ B }

still not getiing what i want. I have searched the archive, but no luck.
thanx for any help.
-- 
  Mansour Al-Aqeel
  mansour77 at ownmail.net

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