"Simon Marlow" writes:

...

Most of the time it's unnecessary to use an explicit Int#. If your Int is in a data structure, you can use

{-# UNPACK #-} !Int

which is portable, and compiles to an unboxed Int in GHC >= 6.2.

Is this different from !Int and -funbox-strict ?

(I.e., should I change from this to UNPACK pragmas?)

They both have the same effect, but I prefer to put these hints in the source code which is why I prefer to use {-# UNPACK #-} rather than the command-line flag. Also, sometimes it is necessary to have fine-grained control over which fields are unpacked. Cheers, Simon