I wrote this to Darrin, but didn't CC cafe:
On Mar 17, 2010, at 9:20 PM, Darrin Chandler wrote:
type Cartesian_coord = Float
type Latitude = Float
type Longitude = Float
data Point = Cartesian (Cartesian_coord, Cartesian_coord)
| Spherical (Latitude, Longitude)
type Center = Point
type Radius = Float
data Shape = Circle Center Radius
| Polygon [Point]
This obviously stinks since a Polygon could contain mixed Cartesian
and
Spherical points. Polygon needs to be one or the other, but not mixed.
My suggestion would be to use an alternate representation of
"spherical" points in terms of polar coordinates, and then to
normalize and mix at will:
type Theta = Float
type Radius = Float
data Point = Cartesian (Cartesian_coord, Cartesian_coord)
| Polar (Theta, Radius)
normalize_point :: Point -> Point
normalize_point Cartesian x y = Cartesian x y
normalize_point Polar t r = Cartesian x y where x = r * cos t; y = r *
sin t;
It really depends on what you want to do with your points. If you
want to do linear algebra, you might want your points to depend on a
basis, for example. But your "spherical" points don't really form a
basis in three-space, or even over all of two-space._______________________________________________
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