[Haskell-beginners] Meaning of '!' in record defintion? UNPACK?

[Thomas Davie]

On 26 Feb 2009, at 12:07, Colin Paul Adams wrote:

>>>>>> "Thomas" == Thomas Davie <tom.davie at gmail.com> writes:
>
>    Thomas> The {-# UNPACK #-} tells the compiler that it can unpack
>    Thomas> the Int – meaning that a Position will be neatly packed
>    Thomas> into 12 bytes.
>
> What would be the difference if there was no UNPACK pragma?

The tag in the Ints would be included in the structure created, with  
UNPACK, they would not.

Bob