Re: [Haskell-cafe] 3 level hierarchy of Haskell objects

Hi, Patrick Browne wrote:

Haskell type classes seem to be signature only (no equations, ignoring default methods) so in general they provide an empty theory with no logical consequences.

Note that many type classes in Haskell have equations annotated as comments. For example, the monad laws are mentioned in the documentation of the Monad type class: http://hackage.haskell.org/packages/archive/base/latest/doc/html/Prelude.htm... In this context, see also the current thread about what equations we can expect to hold for Eq instances: http://thread.gmane.org/gmane.comp.lang.haskell.cafe/99517 Tillmann