Shiro Kawai <xxxxxx@gmail.com> schrieb am Mi., 5. Okt. 2016 um 01:55 Uhr:

> a record belonging to a supertype
> exposes its instance payload not only through its own accessor, but
> also through the accessors of any subtypes.

Isn't it reversed? Supertype's accessor can retrieve the instance's payload
of its subtype, but the other way around doesn't seem to work.

I am equally confused on what this SRFI wants to specify. In http://srfi-email.schemers.org/srfi-137/msg/3939333 you, John, write that the parent accessor should be able to retrieve the payload from an instance of one of its subtypes.

This (the parent accessor can access the payload of a subtype) is certainly what is needed for using this SRFI in the real world. For example, it would be impossible to implement a record-type system à la SRFI 131 and 136 on top of SRFI 137 if it didn't provide this.

And if not, one would hardly call the subtype instances "subtypes" of the parent type.

Marc