On Thu, Mar 18, 2010 at 12:17 PM, John Meacham <j...@repetae.net> wrote: > 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 > _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
