Consider
newtype Foo = Foo Int
lift :: (Int -> a) -> Foo -> a
lift f (Foo x) = f x
Now, I'd expect this to compile with -O2 down to something like
lift f = f `cast` (Foo -> a)
but it doesn't.
It seems that GeneralizedNewtypeDeriving assumes that these two things *are*
equivalent, and it just
On Thu, Jul 8, 2010 at 3:25 PM, J. Garrett Morris wrote:
> Hello everyone,
>
> I'm currently in the process of wrapping a C API, and I've run across
> an interesting possibility. Basically, the C API exposes non-blocking
> versions of some potentially long-running operations, and will invoke
> a
Hello everyone,
I'm currently in the process of wrapping a C API, and I've run across
an interesting possibility. Basically, the C API exposes non-blocking
versions of some potentially long-running operations, and will invoke
a callback to indicate that the long running operation has finished.
Fo
On Thu, Jul 08, 2010 at 04:49:00PM +0200, Daniel Fischer wrote:
> If there are more pitfalls, is there any chance of getting a function which
> reinterprets the bit-patterns?
Hi, you can do something like this (untested):
castWordToFloat :: Word32 -> Float
castWordToFloat w = unsafePerformIO $ d
On Thursday 08 July 2010 18:15:44, Ian Lynagh wrote:
> On Thu, Jul 08, 2010 at 04:49:00PM +0200, Daniel Fischer wrote:
> > unsafeCoerce# :: Word64# -> Double# ?
> >
> > By the docs, that isn't supposed to work. Is it not supposed to work
> > only because it's not value-preserving (unsafeCoerce# 1##
On Thu, Jul 08, 2010 at 04:49:00PM +0200, Daniel Fischer wrote:
>
> unsafeCoerce# :: Word64# -> Double# ?
>
> By the docs, that isn't supposed to work. Is it not supposed to work only
> because it's not value-preserving (unsafeCoerce# 1## /=## 1.0##) or are
> there more pitfalls?
It can fail t
The docs for unsafeCoerce# say:
"The following uses of unsafeCoerce# are supposed to work (i.e. not lead to
spurious compile-time or run-time crashes):
# Casting any lifted type to Any
# Casting Any back to the real type
# Casting an unboxed type to another unboxed type of the same size (but not
