Re: Equality and hashing for new datatypes

[Robby Zambito]

Taylan Kammer <taylan.kammer@gmail.com> writes:

> On 23.06.2023 00:45, Philip McGrath wrote:
>> 
>> Thanks, but this is the opposite of what I want to do. The library I'm 
>> porting 
>> already supports creating tables with custom equality and hashing functions. 
>> What I'm trying to do is make the standard `equal?` procedure recognize when 
>> two of my table values are semantically the same even if internal 
>> implementation details differ.
>> 
>> (Note also that SRFI 69 and other libraries provide *mutable* hash tables. 
>> The 
>> Racket-on-Chez library I'm porting provides immutable hash tables, more 
>> properly Hash Array Mapped Tries, as made famous by Clojure.)
>> 
>> -Philip
>
> Ah, apologies then.  As far as I know, there's no other way to do that in 
> Guile
> than with GOOPS, which you've already mentioned.
>
> In standard Scheme there's no way to do it at all.  I don't think there's even
> an SRFI for it (I just searched a bit, out of curiosity, couldn't find 
> anything).

YASOS can be implemented in standard Scheme[1], but it has the same
limitations as GOOPS in this context. It cannot really be "injected"
into existing modules AFAIK.  

Footnotes:
[1]  https://notabug.org/PangolinTurtle/yasos-r7rs