MetaFun - Pragma ADE

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The original label macros permits us to align the label at positions, 4 corners and 4 points halfway
the sides. It happens that circles are also composed of 8 points. Because in most cases the label is
to be positioned in the direction of the center of a curve and the point at hand, it makes sense to
take circles as the starting points for positioning the labels.
To help us in positioning, we define a special square path, freesquare. This path is constructed
out of 8 points that match the positions that are used to align labels.
path freesquare ;
freesquare := ((-1,0)--(-1,-1)--(0,-1)--(+1,-1)--
(+1,0)--(+1,+1)--(0,+1)--(-1,+1)--cycle) scaled .5 ;
We now show this free path together with a circle, using the following definitions:
drawpath fullcircle scaled 3cm ;
drawpoints fullcircle scaled 3cm ;
drawpointlabels fullcircle scaled 3cm ;
currentpicture := currentpicture shifted (5cm,0) ;
drawpath freesquare scaled 3cm ;
drawpoints freesquare scaled 3cm ;
drawpointlabels freesquare scaled 3cm ;
We use two drawing macros that are part of the suite of visual debugging macros.
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As you can see, point 1 is the corner point that suits best for alignment when a label is put at point 1
of the circle. We will now rewrite thefreelabel in such a way that the appropriate point of the
associated freesquare is found.
vardef thefreelabel (expr str, loc, ori) =
save s, p, q, l ; picture s ; path p, q ; pair l ;
s := thelabel(str,loc) ;
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Free labels A few applications
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