Template Haskell is frightfully good and we want to get rid of cpp and use it instead, but there's one tiny problem, namely that for cpp it is possible to define variables on the command line (-DSIMON=MARLOW and so on) while with Template Haskell it doesn't seem to be. Could there be some kind of dictionary, like the cpp environment variables, which the Template Haskell code has access to? One obvious way would be to accept the -D/-U arguments, and provide Haskell functions which look at them. Of course one /could/ presumably use System.getArgs and analyse the arguments to ghc oneself, but that would mean making guesses about the current GHC syntax. In the meantime we shall still replace cpp with Template Haskell, but find another way. Thanks for Template Haskell!