Re: If records are not sequences, why does aref work on records?

[Philipp Stephani <p.stephani2@gmail.com>]

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Noam Postavsky <npostavs@users.sourceforge.net> schrieb am Fr., 7. Apr.
2017 um 23:03 Uhr:

> On Fri, Apr 7, 2017 at 4:49 PM, Drew Adams <drew.adams@oracle.com> wrote:
> >
> > I don't understand the backward-compatibility argument.
> > A record type has not existed before.  When/where do we
> > already have `aref'/`copy-sequence' being applied to
> > something other than a sequence/array?
>
> Up until the recent changes, the things produced by cl-defstruct
> make-foo functions were vectors with the first element being the
> symbol 'cl-struct-foo'. So they could be indexed with aref and copied
> with copy-sequence. Now they are "record" objects, but we don't want
> to break code that uses aref and copy-sequence on them.
>
>
While the manual mentions that vectors or lists are used, it doesn't say
that the sequence functions can simply be used. Rather, the implementation
as sequence is an implementation detail that users shouldn't rely on.
cl-defstruct even creates a copy-FOO function to copy structures, which
should be used instead of copy-sequence. Therefore, I think it's fine to
not allow copy-sequence and aref on structure types any more, if this
change is properly documented.

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