[racket] objects as hash keys

Thansk for the answer, I didn't notice this part of the doc.
In fact the (make-hasheq) doesn't fit because the objects needs to be
inspect with equal? to find a match.
It seems it is not possible this way, as writted in the doc.
Thanks anyway.


> From the docs (3.13 Hash Tables):
> Caveat concerning mutable keys: If a key in an equal?-based hash table is  
> mutated (e.g., a key string is modified with string-set!), then the hash  
> table’s behavior for insertion and lookup operations becomes unpredictable.
> 
> Try make-hasheq instead of make-hash, that should work here.
> 
> 
> 
> On Fri, 19 Oct 2012 17:57:41 +0200, Ted <tedr56 at gmail.com> wrote:
> 
> > Hi the list,
> > I was wondering for my midi/osc -> event mapping project if it was
> > possible to put objects instances (with racket/class) as hash keys.
> > I tried and it worked. The problem is, I pushed further and when I
> > change object fields, the hash can't find my key anymore, despite I see
> > it in.
> >
> > For the record:
> >
> > (require racket/class)
> >
> > (define test%
> >     (class object%
> >         (inspect #f)
> >         (init-field
> >             address
> >         )
> >         (define/public (getAddress)
> >             address
> >         )
> >         (define/public (setAddress n)
> >             (set! address n)
> >         )
> >         (super-new)
> >     )
> > )
> >
> > (define testy (new test% (address 12)))
> > (define testH (make-hash))
> > (hash-set! testH testy (send testy getAddress))
> >
> >> testH
> > #hash((#(struct:object:test% 12) . 12))
> >
> >> (send testy setAddress 13)
> >> testH
> > #hash((#(struct:object:test% 13) . 12))
> >> (hash-has-key testH testy)
> > #f
> >> (hash-ref testH testy)
> > hash-ref: no value found for key: (object:test% 13)
> >
> > That's an odd response. I know it's an odd request too, but if anyone
> > could help me on this, even it I have to use an other solution.
> >
> > Thanks in advance.
> >
> > Ted
> 
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