| Here is some strange question:
| how to force the compiler to evaluate some things more statically
| and to convert some run-time errors into the compile-time ones?
Not strange at all. It would be quite reasonable to have some way
to tell the compiler 'evaluate this to a static value'. I'd suggest
doing it via a pseudo-function
static :: a -> a
which behaved like the identity function, except that it evaluated
its argument rather eagerly at compile time. Implementing it would
be a little delicate (because inlining is already a delicate part of
GHC) but would not take much code.
About converting run-time to compile-time errors, as others have
said, some functions are legitimately bottom. But think about assertions:
f x = assert (p x) (...x...)
where assert :: Bool -> a -> a
If the boolean is False, you get an error message pinpointing the
line in the file. Now, a function with an assert that always fails
is indeed a good candidate for a compile-time error message.
Again, this is a modest extension, and GHC already has a little-known
assert feature.
But both of these are yet more non-standard features to add.
Life is short. Are these features that would be useful to lots of people?
Simon
