> A newtype can only have one constructor, with one argument, and is > essentially a wrapper for that argument type. > > In the general case, you want to use "data" instead of "newtype": > > data Rectangle = R Int Int
I'm sure there's a trivial explanation for this, but here's something that I've always kind of wondered about: Given a single constructor type like "data X = X A B C" can't that be transformed into "newtype X = X (A, B, C)"? There must be some difference, because if there weren't we could transform all single constructor types that way, and dispense with newtype entirely. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
