Hi
Top-level unboxed values would then behave just like #define constants, in fact. This is certainly possible, it would just add complexity to the compiler in various places.
Yes, that was all I was thinking of. I'm not suggesting that these things actually get implemented, but it did seem a strange restriction that it would have been impossible to define something like realWorld# in Haskell without baking it into the compiler.
What would you expect to happen for this?
fib :: Int -> Int# fib n = ...
x :: Int# x = fib 100#
'x' cannot be bound to a thunk. So the top-level computation would have to be evaluated eagerly. But when? Perhaps when the program starts?
Yes, when the program starts seems perfectly sensible - and mirrors what happens in C, I believe. My particular use of this construct was to introduce a little bit of abstraction so that the same code could be compiled with GHC and Hugs simply by switching in a different set of definitions - and still perform optimally in GHC. But some CPP does just as well :-) Thanks Neil