On Thu, 30 Jun 2005, Jacques Carette wrote:
Henning Thielemann wrote:
Data Orientation = Row | Column Data Vector a = Vector Orientation [a]
In the first mail you wrote "9. There are row vectors and column vectors, and these are different types. You get type errors if you mix them incorrectly."
I interpreted that you want to encode the information Row or Column into the type. This sounds reasonable to me because multiplying e.g. a column vector by a matrix is so obviously wrong that it should be detected statically.
Sorry, I should have been more precise, I used too straightforward an encoding from Maple (which is dynamically typed) into Haskell. I should have used the usual type-trickery to encode the Orientation as 2 different types, to have ``types reflect values''.
You mean phantom types? data Vector orient a = Vector [a] I'm excited to add lots of new orientations then! :-]