Laurdag 16. januar 2010 22.40.17 skreiv Malcolm Wallace:
I'm thinking the syntax would be something like AlternativePrelude="MyPrelude".
There is a general principle that the semantics of a program should be completely described by the source code itself, and not dependent on options that may or may not be specified elsewhere. Hence, the idea of adding {-# LANGUAGE #-} pragmas, so that the source code is self- contained.
Specifying {-# LANGUAGE NoImplicitPrelude #-} together with "import MyPrelude" satisfies this principle, as does {-# LANGUAGE AlternativePrelude="MyPrelude" #-} in all files where it matters. But the difference in usability is slight.
If you are suggesting that {-# LANGUAGE AlternativePrelude="MyPrelude" #-} should somehow escape the scope of the module it appears in, then I think we heading for less firm ground.
Regards, Malcolm
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Having a LANGUAGE pragma, or indeed any pragma, escape the module it's used in would be pretty silly, wouldn't it? In principle I'm a fan of the LANGUAGE pragmas. Self-contained source is usually much easier to read that source that depends on whatever command the author used to build the thing. However, the option to set language extension globally is still available, either as an option to the compiler when building, or in the cabal file describing the package. Allowing an alternative prelude in this fashion makes it easier to switch out the standard for alternatives in existing projects just to see what might happen, how things are changed or just for giggles. It might not be advisable to do so in code you plan on unleashing on the world, but it would make experimenting with alternatives cheaper than it currently is. -- Sjur Gjøstein Karevoll