Hei everybody,

	here http://github.com/bolthar/intersect/ is my solution. You will need
freightrain (http://github.com/bolthar/freightrain/ to run it.
intersect.rb is a script that can be run with an argument, which is the
path to the filename containing the shapes definition. The file
'testfile' in the lib directory is an example of the syntax. 
intersect_gui.rb launches a GUI application that you can play with.

-- 
Andrea Dallera
http://github.com/bolthar/freightrain
http://usingimho.wordpress.com


On Sat, 2010-05-29 at 08:29 +0900, Daniel Moore wrote:
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> 
> ## Geometric Intersections (#233)
> 
> HIRB
> 
> This week's quiz is to detect the intersections of various geometric
> elements: circles, lines, and polygons.
> 
> A circle is defined by a point and a radius.
> 
> point = [6, 3]
> radius = 5
> a = Circle.new(point, radius)
> 
> A line can be defined by two points, or a point and a slope.
> 
> p1 = [0, 0]
> p2 = [4, 2]
> line = Line.new(p1, p2)
> slope = 0.5
> line = Line.new(p1, slope)
> 
> A polygon can be defined as a collection of points.
> 
> b1 = [2, 9]
> b2 = [1, 3]
> b3 = [7, 5]
> 
> b = Polygon.new(b1, b2, b3)
> 
> def intersect(a, b)
>   # Should return true or false indicating whether or not
>   # a and b intersect. a and b can be any circle, line or
>   # polygon.
> end
> 
> You may also find it more natural to define a.intersect(b) or
> b.intersect(a). The relation should be symmetric and reflexive, though
> not transitive.
> 
> Which methods you choose to add to the geometric elements is up to
> you, the only hard requirement is that the intersect method(s) return
> the correct truth values.
> 
> Have fun!
> 
> Extra Credit: handle the "edge" cases of the polygon comprised of one
> point (a single point) or two points (a line segment).
> 
> Extra Extra Credit: Provide a graphical and colorful output indicating
> intersections.

>