MetaFun - Pragma ADE

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1.19 Cutting and pasting
When enhancing or building a graphic, often parts of already constructed paths are needed. The
subpath, cutbefore and cutafter operators can be used to split paths in smaller pieces. In order
to do so, we must know where we are on the path that is involved. For this we use points on the
path. Unfortunately we can only use these points when we know where they are located. In this
section we will combine some techniques discussed in previous sections. We will define a few
macros, manipulate some paths and draw curves and points.
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This circle is drawn by scaling the predefined path fullcircle. This path is constructed using
8 points. As you can see, these points are not distributed equally along the path. In the following
graphic, the second and third point of the curve are colored red, and point 2.5 is colored yellow.
Point 0 is marked in black. This point is positioned halfway between point 2 and 3.
It is clear that, unless you know exactly how the path is constructed, other methods should be
available. A specific point on a path is accessed by point ... of, but the next example demonstrates
two more alternatives.
path p ; p := fullcircle scaled 3cm xscaled 2 ;
pickup pencircle scaled 5mm ;
draw p withcolor .625white ;
draw point 3 of p withcolor .625red ;
draw point .6 along p withcolor .625yellow ;
draw point 3cm on p ;
Welcome to MetaPost Cutting and pasting
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