# TeXnical notes

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Sometimes I find a solution to a TeXnical problem, and I think everybody should know about it. Some of these things are totally obvious, but (as far as I know) non-standard.

## How to draw the Fox-Artin wild arc with pstricks

tex pdf (pdf contains only the resulting image)

## Placing labels on arrows in XY-pic

(I learned this trick from Aaron Lauda; I haven't seen it documented anywhere)

`\xymatrix{asdfasdf \ar[r]^{f} & a }`

produces the label "f" in a stupid place, half-way between the centers of the two entries, instead of where you'd like it to be, half-way along the arrow. One way to handle this is to do something like

`\ar[r]^(.7){f}`

but that is fairly unsatisfying because you have to calibrate the (.7) by eye. There is another way, which is to use

`\ar[r]^-{f}`

which will automatically place the label "f" half-way along the arrow. If you want the label .7 of the way along the arrow, you can do

`\ar[r]^-(.7){f}`