arc_slot OpenSCAD example

arc_slot.scad

use <FunctionalOpenSCAD/functional.scad> 
// https://github.com/thehans/FunctionalOpenSCAD/blob/master/functional.scad

module arc_slot(R,r,a) {
	polygon(concat(
		arc(r=R-r, angle=a,    offsetAngle=0,     c=[0,0], endpoint=false),
		arc(r=r,   angle=-180, offsetAngle=a-180, c=R*[cos(a),sin(a)], endpoint=false),
		arc(r=R+r, angle=-a,   offsetAngle=a,     c=[0,0], endpoint=false),
		arc(r=r,   angle=-180, offsetAngle=0,     c=[R,0], endpoint=false)
	));
}

$fs = 0.5;
$fa = 1;
arc_slot(10,3,90);