David Van Horn scripsit:
> If you consider R5RS to be a compatible extension of R4RS (which I do),
> then R4RS is the most widely supported Scheme standard. If you consider
> R4RS to be a compatible extension of R3RS (which I do), then R3RS is the
> most widely supported Scheme standard.
Well, not quite compatible; there is a large overlap, as I noted in an
earlier posting, but not complete. Here's a potted history of the
changes (may contain errors):
Removed in R3RS: -1+, 1+, <=?, <?, =?, >=?, >?, append!,
named-lambda, object-hash, object-unhash, rec, sequence,
string-null?, string=?, substring-fill!, substring-move-left!,
substring-move-right!
Added in R3RS: boolean?, delay, denominator, force, numerator,
procedure?, quasiquote, sqrt
Removed in R4RS: exactness, fix, flo, heur, int, last-pair, nil,
polar, radix, rat, rect, sci, t
Added in R4RS: list?, peek-char, string
Removed in R5RS: (nothing)
Added in R5RS: call-with-values, define-syntax, dynamic-wind,
eval, interaction-environment, let-syntax, letrec-syntax,
null-environment, port?, scheme-report-environment,
values, call-with-values, define-syntax, dynamic-wind,
eval, interaction-environment, let-syntax, letrec-syntax,
null-environment, port?, scheme-report-environment, values
> And what about IEEE/ANSI Scheme? You left that off. It is the most
> mature and long standing Scheme standard (and is more or less R4RS). It
> was approved in 1990 and reaffirmed in 2008.
I know nothing about IEEE Scheme except what it says in the back of R5RS.
I have never seen a copy of the standard, nor do I know of anyone who
openly admits to possessing one. To buy one would be $187 at present,
which is rather more than I care about it.
> The small language has to be supported by 90%(!) of the electorate.
Indeed. I am no fan of minority rule, but there it is. See the .sig.
> That is a nearly unreasonable level of agreement of what should be in
> Scheme. I think we should start with something very well established (I
> think IEEE Scheme fits the bill)
I agree (and so does the SC, which currently mandates IEEE + modules +
macros), but it will only take 10% of radical minimalists who want Small
Scheme (like, no procedures at all) to be Smallest Conceivable Scheme
to shoot that down.
> and very conservatively add the
> features and requirements that make extending that language to the level
> of R6RS possible.
I'm willing to say that the modest increase that R5RS represents over R4RS
is worth having, thus using R5RS as a starting point.. Note that some of the
improvements, like dynamic-wind,
have pervasive effects.
> Just to be clear: I want a R6RS-like language. I do not want to program
> in R3RS Scheme.
I don't think anybody does.
> Counting bound identifiers in a language with macros and modules (which
> are required by the working group charter) is not meaningful.
It dictates the size of the standard, which is a fetish much worshipped
in these parts. More seriously, it also specifies, as Joe Marshall said,
what is the minimum function that a user can expect to get.
> I never said we need a standard as tiny as this. I was just trying to
> outline what it means to be "Scheme". I think it is reasonable to say
> any system not supporting that subset is not a Scheme. This is a useful
> reference point in a standardization discussion.
Fair enough.
> I do think if you take this language, add syntax-rules macros and the
> R6RS library system specialized for this sublanguage (which will be
> quite simple), and figure out how semantic and lexical extension are
> going to be allowed for,
> you have something which might be able to
> garner 90% support while still allowing the consistent and compatible
> extension of that language to an R6RS-like standard.
Do you think that R5RS unmodified would garner 90% as Small Scheme
today? I doubt it.
--
John Cowan [email protected] http://ccil.org/~cowan
And now here I was, in a country where a right to say how the country should
be governed was restricted to six persons in each thousand of its population.
For the nine hundred and ninety-four to express dissatisfaction with the
regnant system and propose to change it, would have made the whole six
shudder as one man, it would have been so disloyal, so dishonorable, such
putrid black treason. --Mark Twain's Connecticut Yankee
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