[Xy-pic] half-solid ellipse

Chris Brav brav at mast.queensu.ca
Sun Mar 27 21:14:23 CEST 2005

hi. i'm trying to make 2D cobordism diagrams. i like to draw them from
left to right, with solid circles on the in direction (left-hand) and half-solid,
half-dotted circles on the out direction (right-hand), with the solid half
"out front" and the dotted half "behind". a. lauda's code does this for diagrams drawn
from top to bottom, but i can't get it to work from left to right.

here is my code:

\[ \xy
"TTL";"A" **\crv{(5,8) & (3,4)};
"A";"TR" **\dir{-};
"BBL";"B" **\crv{(5,-8) & (3,-4)};
"B";"BR" **\dir{-};
"TBL";"BTL" **\crv{(3,2) & (3,-2)};
\endxy \]

the trouble is line #3. i presume =:a() is supposed to set an angle, but
no matter what angle i try, i can't get rid of the extra solid part
showing from "behind".

any suggestions?

chris brav

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