Dimitry Golubovsky wrote:

The section 8.1.1 of the GHC User's Guide says this:

The following unboxed types may be used as basic foreign types (see FFI Addendum, Section 3.2): Int#, Word#, Char#, etc

Does this mean that when declaring a foreign function import for a C function

int fun(int)

I may write

foreign import ccall "bla.h fun"

fun :: Int# -> Int#

instead of using CInt?

Yes you can do this, but it's non-portable (of course). In many cases GHC's optimiser will remove unnecessary boxing anyway.

Are there any examples of using unboxed types with FFI?

Not any more, because nowadays we prefer to use the portable version instead. There might be a few examples of passing MutableByteArray# around, though. Cheers, Simon