Re: What are the long-term goals for R7RS in Chicken?

[Lassi Kortela]

> Currently you can switch to R7RS more by installing the egg and running csc
> with "-R R7RS -X R7RS", which is a mouthful, and could be abbreviated, that
> doesn't look to me like too much hassle.
>
> Anybody for a "-r7rs" option that does the above?

+1 for an easy command line flag!

Gauche and Sagittarius Scheme have an "-r" flag so you can run 
"sagittarius -r 6" or "gosh -r 7". Using one flag gives simple upward 
compatibility to "-r 8", "-r 9" in the future, and also non-RnRS 
standards or modes, should the need arise. Neither csc nor csi is yet 
using the "-r" flag for anything, so the uniformity would be nice. It 
also has nice symmetry with the upper case "-R" flag for extensions.

> A good question. I think the Chicken "native" language and module system
> is likely to be used more often than a R7RS mode, so I don't think there are
> any attempts to make Chicken "more R7RS". As you say, the differences
> are not that substantial.

If there are few substantial differences, it would be a boon to writing 
portable code if the same syntax is eventually used as for standard R7RS 
libraries, and the same filename conventions are supported as other R7RS 
implementations (the .sld filename extension for an R7RS library is 
becoming a de facto standard). You already support (include "...") and 
(cond-expand ...) in a similar manner as R7RS.

Here's how a typical module would look, before:

;;-----------------------------------------------------------------------------
(module lowdown

  (markdown->sxml
   markdown->sxml*
   markdown-sxml->html-sxml
   markdown->html
   markdown-html-conversion-rules*)

  (import scheme)

  (cond-expand
   (chicken-4
    (import chicken)
    (use data-structures
         irregex
         srfi-1
         clojurian-syntax
         comparse
         sxml-transforms
         lowdown-lolevel))
   (chicken-5
    (import (chicken base)
            (chicken irregex)
            (scheme)
            (srfi 1)
            (clojurian syntax)
            (comparse)
            (lowdown lolevel)
            (sxml-transforms))))

  ...code here...)
;;-----------------------------------------------------------------------------

And after:

;;-----------------------------------------------------------------------------
(define-library (lowdown)
  (export markdown->sxml
          markdown->sxml*
          markdown-sxml->html-sxml
          markdown->html
          markdown-html-conversion-rules*)
  (cond-expand
   (chicken-5
    (import (scheme base)
            (chicken base)
            (chicken irregex)
            (srfi 1)
            (clojurian syntax)
            (comparse)
            (lowdown lolevel)
            (sxml-transforms))))
  (begin ...code here...))
;;-----------------------------------------------------------------------------

Functors could use the existing syntax:

(functor (squaring-functor (M (multiply))) (square)
  (import scheme M)
  (define (square x) (multiply x x)))

or spell it `define-functor` for consistency.

It should be possible to preserve the old (module ...) and (functor ...) 
syntax for backward compatibility so current modules keep working with 
no code changes.