Re: [Scheme-reports] Ratification vote for R7RS-small

On Wed, Apr 24, 2013 at 8:24 PM, Sam TH <sam@x> wrote:

On Wed, Apr 24, 2013 at 4:44 AM, Alaric Snell-Pym
<alaric@x> wrote:
> I hear the complaints from
> people that our rejection of R6RS has been a mistake, but that was the
> scope of the requirements laid down by the Steering Committee

Certainly the charter didn't *require* R6RS compatibility, but it
didn't *prohibit* it. For example, the decisions not to make the
module system or the error system or the struct system compatible were
decisions that the working group took that could have gone the other
way.

Sam, thank you for providing a rationale with your vote and for

including specific points.

I think it's somewhat hypocritical to cite these specific examples

though. R6RS chose to break compatibility with the widely

implemented and used SRFI-9 and SRFI-23, and provided a

module system incompatible with R5RS and most existing module

systems. We were thus forced into a decision that was incompatible

with one or the other either way. You can of course disagree with

our decisions, but you can't take the moral high ground here.

The module system compatibility perhaps needs clarification. The

primary goal of the WG1 charter - which I strongly agree with -

was to improve Scheme compatibility. To provide a common

ground for implementations to share code. To this end, by far the

most important property is that the module system be supported

and that it not be second class. You should be able to import

native modules from portable modules and vice versa, and there

should be no loss of performance.

As mentioned already, R6RS actually makes it impossible to

use existing R5RS code unmodified, but more than that the

versioning and phasing features make it impossible to integrate

with most existing module systems. R7RS has neither of these

problems. Further, since we moved the complex and controversial

versioning and phasing issues to WG2, choosing a superficially

different syntax actually improves R6RS compatibility. You can

support both library and define-library as in Sagittarius, so it's

misleading to say R7RS modules are incompatible with R6RS.

Again, the decisions are debatable, but the time for debate is

long over. The charter was finalized over three years ago, the

formal comments period ended over half a year ago, and the

community provided constant feedback in the interim. You can

disagree now, but keep in mind it was R6RS that broke backwards

compatibility and hampered forwards compatibility long before

any of this.

Alex