Hi all, Sorry to dig up an old topic, but I think this is an important one. (at least it is for me). I have run into a problem recently. I am writing a debugger for Haskell. It is based on a source-to-source transformation. The important bit is that the type of functions changes under the transformation. If you want to debug calls into the Standard Prelude (yes this is useful) then a transformed Prelude must be used. The idea being that a transformed program imports a transformed Prelude. That's okay, my debugger can transform all of the Standard Prelude since it is just a Haskell module (with provisions for primitive functions of course). The problem is that when I replace the Standard Prelude with a transformed Prelude the defaulting mechanism doesn't work anymore. What I would like is that the defualting rules refer to the classes in my version of the Prelude, not the Standard Prelude. I am using ghc version 5.03, and I don't think -fno-implicit-prelude can help here. I do think that this issue is independent of the Haskell environment, and more an issue of the design of the language. Now there have already been some discussions about replacing the Standard Prelude with a non-Standard Prelude. The trick being that a fair degree of the language definition makes use of things in the Standard Prelude. See for example: Dylan Thurston Replacing the Prelude http://www.haskell.org/pipermail/haskell-cafe/2002-May/003032.html Primitive types and Prelude shenanigans http://www.haskell.org/pipermail/haskell-cafe/2001-February/thread.html#1641 I'm fond of the idea proposed by Marcin 'Qrczak' Kowalczyk: May I propose an alternative way of specifying an alternative Prelude? Instead of having a command line switch, let's say that 3 always means Prelude.fromInteger 3 - for any *module Prelude* which is in scope! That is, one could say: import Prelude () import MyPrelude as Prelude IMHO it's very intuitive, contrary to -fno-implicit-prelude flag. Presuming of course that defaulting would follow this path and refer to the new Prelude. I'm wondering if any further progress has been made towards this? Or perhaps someone can think of a temporary solution to my problem? Cheers, Bernie.