Re: records as s-expressions

[Marius Vollmer <mvo@zagadka.de>]

Thamer Al-Harbash <tmh@whitefang.com> writes:

> On Thu, 16 Oct 2003, Marius Vollmer wrote:
>
>> Yes.
>>
>> One other thing that just occured to me: how does 'read' find the
>> record creator from the type name?
>
> Good point. I can't see how this would work by putting it in the
> reader.

Me neither.  We can't easily solve the general problem (writing _all_
record types in a readable way by default), but we could make it easy
for the user to implement readable writing for selected record types.

Something like this:

  (define r (make-record-type foo '(a b) readable-record-printer))
  (register-record-reader 'foo foo)

where readable-record-printer will print a record as

  #,(foo a: ... b: ...)

and register-record-reader will use define-reader-ctor to be able to
read the record back in.

> Here's the real problem though:

That's not serious: this only happens because the default record
printer uses display instead of write.

> However a problem occurs when dealing with SMOBs or types which
> (read) cannot convert properly.  How is this dealt with in data
> types like arrays? If I print an array, which contains smobs or
> records, from the REPL, how is it converted back when (read) gets it
> again?

This is a separate problem; we don't need to solve it right now.

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