Hi, Trying to get up to speed in Haskell, I'm playing with doing some abstraction in data types. Specifically, I have this:
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.
I could define seperate types for Cartesian and Spherical and seperate
CartesianPoly and SphericalPoly, but that doesn't seem very elegant and
also increases as I add more coordinate systems and shapes. I read a
little on GADTs, et al, but I'm not sure if that's what I want for this
or not.
Any help appreciated!
--
Darrin Chandler | Phoenix BSD User Group | MetaBUG
dwchand...@stilyagin.com | http://phxbug.org/ | http://metabug.org/
http://www.stilyagin.com/ | Daemons in the Desert | Global BUG Federation
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