On Thu, Mar 18, 2010 at 12:17 PM, John Meacham
On Wed, Mar 17, 2010 at 09:20:49PM -0700, Darrin Chandler wrote:
data Point = Cartesian (Cartesian_coord, Cartesian_coord) | Spherical (Latitude, Longitude)
Just a quick unrelated note, though you are probably aware of this, doing
data Foo = Foo (X,Y) means something subtly different than data Foo = Foo X Y and can be less efficient.
On the other hand, the latter is equivalent to: newtype Foo = Foo (X,Y)
A quick way to see they are different is to count the bottoms,
in the first case (where _ is bottom and X is some value) you have the cases
Foo _ Foo (_,_) Foo (X,_) Foo (_,X) Foo (X,X) and in the other case you have Foo _ _ Foo X _ Foo _ X Foo X X
so one has 5 distinct values, and the other has 4, hence they are not isomorphic. All things being equal, this means the second case will be more efficient as there is one less case it needs to distinguish (every potential bottom implys an 'eval' somewhere). Depending on your code, all things may not be equal and there are rare times when the tupled version is more efficient however.
John
-- John Meacham - ⑆repetae.net⑆john⑈ - http://notanumber.net/ _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe