Re: why is Data.Set not a Monad?y

Hi

You could just have used {-# OPTIONS_GHC -fno-implicit-prelude #-} and rebound do.

...

{-# OPTIONS -fglasgow-exts -fallow-undecidable-instances #-}

OPTIONS is obsolescent - new code should use OPTIONS_GHC, etc. (since options are by there nature compiler dependant)

New code should ideally use LANGUAGE: {-# LANGUAGE AllowUndecidableInstances #-} It also means you can't throw in everything (all extensions), but have to be more selective. In some cases you still need to use OPTIONS_GHC though, particularly for # in id's - although hopefully someone will be adding MagicHash soon :-) Thanks Neil