Hi > I by mistake defined a type which did not specify a data constructor > > So the question is what are types with no constructors good for? A > simple example would be appreciated.
They are called phantom types, and can be used for ensuring properties at the type level. I wrote about them in a blog post: http://neilmitchell.blogspot.com/2007/04/phantom-types-for-real-problems.html There are probably better references, but that's the easiest for me to find ;-) Thanks Neil _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
