On Mon, May 1, 2017 at 10:37 AM, Tony Garnock-Jones <tonyg@ccs.neu.edu> wrote:

On 5/1/17 1:26 PM, Levente Uzonyi wrote:
> I presume that a general purpose in-image solution would be more
> complex. String already has too many subclasses (6 in Squeak), while at
> the same time other kind of new subclasses would be welcome too, e.g.
> Strings with 2-byte characters.
> Since these properties are orthogonal, there would be many new
> subclasses to cover all cases.

A classic motivating case for Traits, right?

Alas no. The problem with String's subclasses is that they're binary objects. They have no inst vars in which one can cache a hash. They're juts a flat vector of bytes. If one added a trait to them the system would fail because there's no way to add an inst var to a binary object in the current Smalltalk object representation. hence Levente's very clever idea of hiding the hash in a hidden header word.

Tony

_,,,^..^,,,_

best, Eliot