[Cuis-dev] Uniqueness of Characters (Related to NeoCSV)

[Juan Vuletich]

Hi Folks,

Hilaire had trouble, that he already solved, when updating NeoCSV for 
current Cuis. The root of the problem is that in older Cuis and in 
Smalltalk-80 and Squeak `aCharacter == $,` is guaranteed to mean the 
same as `aCharacter = $,`. In other words, there can exist only one 
instance of any Character. This is no longer in true today in Cuis: `$, 
== $, asUnicodeCodePoint` is false.

In Cuis we have two character like classes. They are polymorphic, and 
the only observable difference is when asking #== or #identityHash.

The question I ask is: How important is this? Do we need or want 
uniqueness of characters? What do other dialects do? Would it make sense 
to give an error or at least a warning when trying to compare with #== 
against a literal character?

It is possible to guarantee uniqueness of characters, but not without 
some work. The easiest way is what Squeak did, having a single, Unicode 
wide, immediate Character class. But this can not be done in pre-Spur 
(V3) images and VMs.

Thanks,

-- 
Juan Vuletich
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