15 Jul
2008
15 Jul
'08
10:54 a.m.
On Tue, 15 Jul 2008, Chris Kuklewicz wrote:
Consider these 3 files:
A.hs:
module A(A) where import B(B) data A = A B
B.hs
module B(B) where import A(A) data B = B A
Main.hs
module Main where import A import B main = return ()
Sooner or later you want generalize your datatypes. Then you can define data A b = A b and you do not need to import B any longer. I do not know if this is a generally applicable approach, but it helped me in some cases. There is still a problem with mutually recursive classes. In the one case where I had this problem, I could solve it the opposite way, namely by turning one type variable into a concrete type, which could represent all values one could represent with the variable type.