On 2012-01-04, at 1:32 PM, John Cowan wrote:

> Marc Feeley scripsit:
>
>> My issue with these feature identifiers is that their semantics is
>> vague.  Are they a feature of the compile-time Scheme system, or
>> run-time Scheme system, or something else?  What can I infer from
>> the "windows" feature?  Is this windows 3.0 or 95 or ...? The only
>> practical use I can see is to determine the filename syntax, but there
>> are better ways to determine this or to isolate from the difference.
>> Also, endianness is not a pure dichotomy (some systems store code one
>> way and data another, some are middle-endian, etc).
>
> The PDP-11 has been dead for at least 15 years.

The ARM is definitely not dead, and probably the architecture with the largest market currently.

>> Are the CPU architectures well defined?  What is the set of features
>> of i386?  Aren't there differences in sub-variants of i386?  So as a
>> programmer, what are the guarantees I have if the feature i386 is on?
>>
>> Can you present a use-case for these feature identifiers?
>
> Not for strictly conforming R7RS-small programs, no.  As I have said,
> the need arises when talking to lower-level software, and the point of
> enumerating them in the standard is to avoid silly incompatibilities:
> "I say 'darwin', you say 'macosx', let's call the whole thing off!"

Which lower-level software and how can I interface to them given that there's no FFI in R7RS-small?

Marc

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