Re: review/merge request: wip-array-refactor

[Andy Wingo <wingo@pobox.com>]

Hello Ludovic :)

On Sun 09 Aug 2009 18:41, ludo@gnu.org (Ludovic Courtès) writes:

> Andy Wingo <wingo@pobox.com> writes:
>
>> The second model is when you already have a wide deployed base. You can
>> make additions to your API and ABI, and deprecated old API or ABI, but
>> you can't remove old API or change the ABI. Incompatible breaks are
>> painful, and the switching-over time is somewhere between a year and
>> three years. The right length of a stable series seems to be about 4 or
>> 5 years.
>
> I'm in favor of sticking to this model, i.e., paying attention to both
> source and binary compatibility.  That sounds important to me as Guile
> is an old piece of software for which users may expect a relative
> stability and clear upgrade path when that is needed.

I agree.

>> I've written lots of code that deals with srfi-4 vectors. I have three
>> kinds of use cases. First is data being shoved around in a
>> dynamically-typed system: dbus messages, gconf values, a system we 
>> at work, etc. Second, but related, is dealing with chunks of data that
>> come from elsewhere, like GDK pixbufs, or GStreamer buffers. Third is
>> hacking compilers, as in Guile itself, or emitting machine code for
>> other machines.
>
> My feeling is that the 1st and 3rd use cases are what bytevectors were
> written for in the first place.

Agreed.

> SRFI-4 is a good fit for the 2nd use case as you're dealing with
> fixed-width native-endianness numbers coming from C code.

Agreed, modulo the possibility for this data to be embedded within some
other stream.

> But in this case, I don't think bytevectors are needed at all.

I think they are needed whenever you want to *do* something with this
data -- i/o for example.

>> In summary... I don't mean to be a bore, but I really don't like the
>> existing unif.c and srfi-4.c. They are painful to understand and to hack
>> on. I think those bits should be merged.
>
> Agreed.

OK, I'll see about merging up until the polymorphic change after the
release.

>> I also think that srfi-4 vectors should be implemented in terms of
>> bytevectors, for the reasons above.
>
> I'm not convinced, but OTOH, I don't think it hurts.
>
> Like Neil, the one thing that I'm not fond of is the switch from
> disjoint SRFI-4 types to polymorphic types, because programming errors
> that currently yield a `wrong-type-arg' error will be silently ignored.
> The SRFI text allows it, but the rationale says that "the use of
> homogeneous vectors allows certain errors to be caught earlier."

OK. Hopefully when I do my merge, the advantages/disadvantages of the
various approaches will be more clear to all of us (including myself).

Cheers,

Andy
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