Hi all, I am pretty new to haskell, but while exploring the haskell module system, I came along some questions. As far as I found out, haskell supports separated namespaces, i.e. every module has its own symbol space. Thus, when defining a class in one module like module A(Foo(f)) where class Foo a where f :: a -> Integer one should be able to define two instances having the same signature, as long as they are in different namespaces module B(bar) where import A(Foo(f)) instance Foo Integer where f x = x bar x = f x module C(tango) import A(Foo(f)) instance Foo Integer where f x = x + 1 tango x = f x As the integer instances of Foo are in separate modules and thus namespaces, one should be able to just import bar and tango module Main(main) import B(bar) import C(tango) main = print( (bar 5) + (tango 4) ) But now, ghc complains about two instances of Foo Integer, although there should be none in the namespace main. I have not found any documentation on why ghc behaves like this and whether this conforms to the haskell language specification. Is there any haskell compiler out there that is able to compile the above example? Thanks for your help Stephan