Neil Mitchell wrote:
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.
IIRC, C only allows compile-time constants (such as 1+1), and C++ has
the behavior you describe (non-constants computed at load time - which
is criticized for nondeterministic order, slow loading having to go
through many areas of memory...)
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