flvector? and fxvector? are missing equal-always? support

[rocketnia]

What version of Racket are you using?
8.12 [cs]

What program did you run?

Welcome to Racket v8.12 [cs].
> (require racket/flonum)
> (define foo (flvector 1.0 2.0 3.0))
> (define bar (flvector 1.0 2.0 3.0))
> foo
(flvector 1.0 2.0 3.0)
> bar
(flvector 1.0 2.0 3.0)
> (equal-always? foo bar)
#t
> (flvector-set! foo 1 20.0)
> foo
(flvector 1.0 20.0 3.0)
> bar
(flvector 1.0 2.0 3.0)
> (equal-always? foo bar)
#f

And the same thing for fxvectors:

> (require racket/fixnum)
> (define bar (fxvector 1 2 3))
> (define foo (fxvector 1 2 3))
> foo
(fxvector 1 2 3)
> bar
(fxvector 1 2 3)
> (equal-always? foo bar)
#t
> (fxvector-set! foo 1 20)
> foo
(fxvector 1 20 3)
> bar
(fxvector 1 2 3)
> (equal-always? foo bar)
#f

What should have happened?

Generally, for types that are defined with attention to equal-always? support, the result of equal-always? doesn't vary when a value is mutated. Since flvectors and fxvectors are mutable, they should only be equal-always? if they're eq?, similarly to mutable strings or vectors.

Alternatively, some mutation operations could be considered to be part of an unsafe API, like unsafe-set-immutable-car!. If that's what flvector-set! and fxvector-set! are considered to be, the present behavior may be correct. But that's not the impression I get from the documentation; I think these were simply types whose equality behavior was overlooked when equal-always? was introduced.

[usaoc]

On top of this: extflonum vectors (I think) and stencil vectors.

[AlexKnauth]

I think this is because it's falling back on Chez Scheme's flvector and fxvector equality.

Perhaps it shouldn't fall back on that when the mode is chaperone-of? or equal-always?.

[AlexKnauth]

I started a branch to work on this here:
https://github.com/AlexKnauth/racket/tree/equal-always-flvector-fxvector

I'll want to add tests before I make it a full PR though.

[AlexKnauth]

I've made a PR here:
#4984

[AlexKnauth]

@usaoc

On top of this: extflonum vectors (I think) and stencil vectors.

Stencil vectors are fixed in #4984, but I can't test whether extflvectors are broken or not because I get "extflvector: unsupported on this platform". What would be needed to test that?

[mflatt]

Extflvectors are supported only on x86/x86_64 BC.