Hi Levente,


hm, I think #= should be always commutative and transitive, everything else is at least confusing ...


Can't we move that "attribute invariant" comparison rather to something like Text >> #sameAs:?


Best,

Christoph

________________________________
Von: Squeak-dev <squeak-dev-bounces at lists.squeakfoundation.org> im Auftrag von Levente Uzonyi <leves at caesar.elte.hu>
Gesendet: Mittwoch, 16. September 2020 15:00:28
An: The general-purpose Squeak developers list
Betreff: Re: [squeak-dev] FormInspector, or also: Text>>#= and its consequences

Hi Christoph,


On Wed, 16 Sep 2020, Thiede, Christoph wrote:

>
> Interesting, I would not have assumed that this would be only about performance, sounded like a more profound design decision to me.

If you have a look at the comment of Text >> #=, you'll find that it's a
design decision (no reasoning though):

= other
         "Am I equal to the other Text or String?
         ***** Warning ***** Two Texts are considered equal if they have
the same characters in them.  They might have completely different
emphasis, fonts, sizes, text actions, or embedded morphs.  If you need to
find out if one is a true copy of the other, you must do (text1 = text2
and: [text1 runs = text2 runs])."


Though equality with Strings is not symmetric;

'foo' asText = 'foo'. "==> true"
'foo' = 'foo' asText. "==> false"

I don't know what relies on Text-String equality, but probably many things
assume that Texts and Strings are somewhat interchangable (remember when
you changed SHParserST80 >> #initializeVariablesFromContext, and Shout ran
into errors because it expected source to be a String but got a Text?)

You can't keep equality with Strings if you change #= because you'll lose
transitivity:

'foo' asText allBold = 'foo'. "==> true"
'foo' asText = 'foo'. "==> true"
'foo' asText allBold = 'foo' asText "==> false"


Should you decide to change #=, remember to change #hash as well, and
rehash all hashed collections with text keys.


Levente

>
>
> If no one sees a problem in changing this behavior, I can try my luck. :-)
>
>
> Best,
>
> Christoph
>
> __________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
> Von: Squeak-dev <squeak-dev-bounces at lists.squeakfoundation.org> im Auftrag von Taeumel, Marcel
> Gesendet: Dienstag, 15. September 2020 16:42:11
> An: squeak-dev
> Betreff: Re: [squeak-dev] FormInspector, or also: Text>>#= and its consequences
> Hi Christoph.
> Performance. Change it, bench it, post the results here. :-) Please specify you machine and try it on a slow RaspPi, too.
>
> Best,
> Marcel
>
>       Am 10.09.2020 20:32:34 schrieb Thiede, Christoph <christoph.thiede at student.hpi.uni-potsdam.de>:
>
>       Hi all,
>
>
>       is there any old thread about the design discussion of how Text>>#= works? (It does not consider attributes for quality.) Has this decision ever been questioned?
>
>
>       Naively and without an overview of any existing components that could rely on this implementation, I would like to question it.
>
>       Why should 'foo' asText allBold be equal to 'foo' asText addAttribute: TextURL new? With the same logic, we could also say that two dictionaries are equal iff they have got the same keys ...
>
>
>       There is even a concrete client in the Trunk suffering from this design decision: Marcel's new FormInspector (and analogously, MorphInspector). It uses
>
>       TextFontReference with a FormSetFont to display a screenshot right in the inspector pane. Unfortunately, the pane is never updated automatically because even if the screenshot changes, the text morph thinks the old text would equal the new one. I'd like to fix that without hacking any workaround into
>       the inspectors.
> Even though this inspector implementation is a bit unusual, in my opinion, it shows that the current Text >> #= implementation might not be a perfect solution.
>
> I'm looking forward to your opinions.
>
> Best,
> Christoph
>
>
>
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