Re: [Haskell-cafe] rewrite rules to specialize function according to type class?

Max Bolingbroke wrote:

2011/2/15 Simon Peyton-Jones :

...

but currently any pragmas in a class decl are treated as attaching to the *default method*, not to the method selector:

I see. I didn't realise that that was what was happening. Personally I find this a bit surprising, but I can see the motivation. Of course, a sensible alternative design would be to have them control the selectors, and then you could declare that you want your default methods to be inlined like this:

{{{ class MyClass a where foo :: a -> a foo = default_foo

{-# INLINE default_foo #-} default_foo = ... big expression ... }}}

I wouldn't necessarily expect this to guarantee inlining for the same reason that the following code doesn't guarantee that foo gets rewritten to <big>: foo = bar {-# INLINE bar #-} bar = <big> It might work with the current implementation (I'm not even sure if it does) but it would always look dodgy to me. Also, what if I write: class MyClass a where foo :: a -> a foo x = default_foo x I assume this wouldn't guarantee inlining?

In any event, perhaps it would be worth warning if you write an INLINE pragma for some identifier in a class declaration where no corresponding default method has been declared, in just the same way you would if you wrote an INLINE pragma for a non-existant binding?

+1 Roman