From @zwj|08 @end|ng |rom gm@||@com  Tue Oct 22 17:14:28 2019
From: @zwj|08 @end|ng |rom gm@||@com (Wang Jiefei)
Date: Tue, 22 Oct 2019 11:14:28 -0400
Subject: [Rd] S4SXP type vs S4 object bit?
In-Reply-To: <CAPLMX9FMdNTDjQSy-HvCUVrn3ph3rh0-YCTrXhFa5FycL8bjLw-113@mail.gmail.com>
References: <CAPLMX9FMdNTDjQSy-HvCUVrn3ph3rh0-YCTrXhFa5FycL8bjLw-113@mail.gmail.com>
Message-ID: <CAGiFhPNv-JvWVC_bhQ5rFzyOJm9nWq_tuqAuJW-9i--swdLgWQ@mail.gmail.com>

Hi Travers,

Just an additional remarks to Michael's answer, if your S4 class inherits
from R's basic types, say integer, the resulting object will be an INTSXP.
If your S4 class does not inherit from any class, it will be an S4SXP. You
can think about this question from the object-oriented framework: If one
class inherits the integer class, what should R do to make all the integer
related functions compatible with the new class at C level?

Best,
Jiefei

On Tue, Oct 22, 2019 at 4:28 AM Travers Ching <traversc at gmail.com> wrote:

> I'm trying to understand the R internals a bit better and reading over the
> documentation.
>
> I see that there is a bit related to whether an object is S4
> (S4_OBJECT_MASK), and also the object type S4SXP (25).  The documentation
> makes clear that these two things aren't the same.
>
> But in practice, will the S4-bit and object type ever disagree for S4
> objects?  I know that one can set the bit manually in C; are there any
> practical applications for doing so?
>
> Thank you
> Travers
>
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[Rd] S4SXP type vs S4 object bit?
Wang Jiefei