[plt-scheme] Self evaluating "objects"

On Mon, 14 Jul 2008 13:01:10 +0300, Jos Koot <jos.koot at telefonica.net>  
wrote:

> Why bother about eval?

Why not ?

> Nevertheless:
>
> From:  
> http://www.r6rs.org/final/html/r6rs-lib/r6rs-lib-Z-H-17.html#node_idx_1266
> See also: http://www.r6rs.org/final/html/r6rs/r6rs-Z-H-4.html#node_idx_52

I've read those.

"A *SUBSET* of the Scheme objects is called datum values. These *INCLUDES*  
booleans, number objects, characters, symbols, and strings as well as  
lists and vectors whose elements are data. Each datum value may be  
represented in textual form as a syntactic datum, which can be written out  
and read back in without loss of information."


> In #lang scheme and mzscheme and pretty-big the value of a procedure is  
> that procedure. There is #!r6rs though, but:


> #!r6rs
> (library (aap)
>  (export)
>  (import (rnrs eval (6)) (rnrs base (6)) (rnrs io simple (6)))
>  (write (eval (lambda (x) x) (environment '(rnrs base (6))))))
>
> writes #<procedure>, which seems not to conform to R6RS, for a procedure  
> is not a datum value.

It seems so, but the subset called "datum values" is not written in the  
sections you quoted.
Nevertheless it seems that the test "which can be written out and read  
back in without loss of information" fail for procedures.