MetaFun - Pragma ADE

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You can define such a pen yourself:
path p ; p := fullcircle xscaled 2cm yscaled 3cm ;
pen doublepen ; doublepen := makepen ((0,0)--(.3cm,.3cm)) ;
pickup doublepen ; draw p ;
Here we define a new pen using the pen command. Then we define a path, and make a pen out of
it using the makepen macro. The path should be a relatively simple one, otherwise METAPOST will
complain.
You can use makepen with the previously introduced withpen:
draw p withpen makepen ((0,0)--(.3cm,.3cm)) ;
and pickup:
pickup makepen ((0,0)--(.3cm,.3cm)) ; draw p ;
You can use makepen and makepath to convert paths into pens and vice versa.
Pens are very important when defining fonts, and METAFONT is meant to be a font creation tool.
Since METAPOST has a slightly different audience, it lacks some features in this area, but offers a
few others instead. Nevertheless, one can try to design a font using METAPOST. Of course, pens are
among the designers best kept secrets. But even then, not every O is a nice looking one.
1.12 Joining lines
The way lines are joined or end is closely related to the way POSTSCRIPT handles this. By setting the
variables linejoin and linecap, you can influence the drawing process. Figure 1.1 demonstrates
the alternatives. The gray curves are drawn with both variables set to rounded.
Welcome to MetaPost Joining lines