Can't help but remind people of this little post I did a couple years 
back on how to add new immediate types:

http://lists.squeakfoundation.org/pipermail/vm-dev/2006-January/000429.html

Cheers,
   - Andreas


On 10/18/2010 4:41 PM, Bert Freudenberg wrote:
> On 18.10.2010, at 13:49, Colin Putney wrote:
>
>> On Mon, Oct 18, 2010 at 1:38 PM, Eliot Miranda<eliot.miranda at gmail.com>  wrote:
>>
>>> I think immediate characters are much more generally useful, especially
>>> considering unicode.  The current implementation of only codes 0 to 255
>>> being == is error-prone.
>>
>> I enthusiastically agree. I think string handling in Squeak is pretty
>> weak, and having efficient Characters would provide a solid basis for
>> improving it.
>
> Disagree.
>
> You don't want to be manipulating single characters if speed matters. Much better to add primitive support to speed up WideStrings.
>
> Also, adding more immediate objects will slow down the system as a whole. I remember changing the tag bit check in the early days of Squeak did have a performance impact. Whether new immediates would result in a net speed win remains to be seen.
>
> - Bert -
>
>
>