The problem is precisely that I cannot create *novel* instances after
redefining the record, apparently because it tries to initialise them
according to the old definition.
2013/3/1 Neale Swinnerton <ne...@isismanor.com>
>
> On Fri, Mar 1, 2013 at 3:44 PM, Joachim De Beule <
> joachim.de.be...@gmail.com> wrote:
>
>> Here is another (real) example:
>>
>> When I change the number of slots in a record, e.g. from
>>
>> (defrecord MyRecord [slot1 slot2] ...)
>>
>> to
>>
>> (defrecord Myrecord [slot1] ...)
>>
>>
>>
> Are you remembering to recreate the *instances* of the records after
> redefinition? I suspect not and this is causing your problem.
>
> I found this somewhat surprising when I first discovered it, but hopefully
> this REPL session illustrates the point...
>
> user> (defrecord MyRecord [slot1])
> user.MyRecord
> user> (def r1 (->MyRecord 1))
> #'user/r1
> user> (defrecord MyRecord [slot1 slot2])
> user.MyRecord
> user> (def r2 (->MyRecord 1 2))
> #'user/r2
> user> r1
> #user.MyRecord{:slot1 1}
> user> r2
> #user.MyRecord{:slot1 1, :slot2 2}
> user>
> user> (type r1)
> user.MyRecord
> user> (type r2)
> user.MyRecord
>
> ; r1 and r2 apparently have the same type, but
>
> user> (= (type r1) (type r2))
> false
>
> ; r2 is a different (jvm) class (because of different classloader
> introduced by redefinition)
> user> (def r3 (->MyRecord 3 4))
> #'user/r3
>
> ; two instances from the same definition *do* have the same type
>
> user> (= (type r2) (type r3))
> true
>
>
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