On Thu, 2009-09-03 at 06:15 +0300, Abdulaziz Ghuloum wrote:
> On Sep 3, 2009, at 6:02 AM, Derick Eddington wrote:
>
> > ;; Will Clinger hates record-type-descriptor because it
> > ;; requires knowing whether the record type was defined
> > via the
> > ;; syntactic or procedural interface.
>
> I don't understand this.
>
> > The below use is not
> > ;; portable, because it's unspecified which interface a
> > ;; particular implementation used to define &condition.
>
> I don't think so. &condition is a condition type as it says
> in the report, and condition types can only be defined using
> define-condition-type.
But it's unspecified whether define-condition-type uses the syntactic or
procedural record definition interface.
> So, (record-type-descriptor &condition)
> has to return the rtd of &condition.
But record-type-descriptor is specified to require its argument to be a
<record name> which is specified to be an expand-time handle or run-time
value. It's unspecified if a <record name> can be either or not. The
record type defined by define-condition-type might be a run-time value,
while the <record name> defined by define-record-type and required by
record-type-descriptor might be an expand-time handle, which leaves me
not knowing if record-type-descriptor will work for &condition because
&condition might be a run-time value.
Here's a better example of the issue:
> (library (L)
(export some-type)
(import (rnrs))
(define some-type
(make-record-type-descriptor 'some-type #F #F #F #F '#())))
> (import (L))
> (record-type-descriptor some-type)
Unhandled exception
Condition components:
1. &who: record-type-descriptor
2. &message: "not a record type"
3. &syntax:
form: (record-type-descriptor some-type)
subform: #f
4. &trace: #<syntax (record-type-descriptor some-type)>
>
How/why are users supposed to know if some-type was defined via the
procedural or syntactic interface?
> > So I
> > ;; have to say, here's another example adding to my
> > dislike of
> > ;; record-type-descriptor.
>
> Your last couple of dislikes were not very well founded. :-)
Hehehehe :) I like flammable topics because they can reveal what
actually burns.
--
: Derick
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