Hello everyone.

Working Group 2 is pleased to announce the first draft of the second part of the R7RS-Large Foundations, the "Procedural Fascicle". This draft encompasses the familiar block programming forms, such as lambda, let, if, or, and set!.

The draft is available here:

https://r7rs.org/large/fascicles/proc/

The biggest new feature is the ability to mix definitions and expressions in bodies, such as the body of a lambda. For example, the following is now valid:

    (define (map f lst)
      (unless (list? lst)
        (error 'map "not a list" lst))
      (define (map* lst acc)
        (if (null? lst)
            (reverse acc)
            (map* (cdr lst) (cons (f (car lst)) acc))))
      (map* lst '()))

We welcome any and all comments on the draft. Anyone can comment by

* Filing an issue on the R7RS-Large issue tracker <https://codeberg.org/scheme/r7rs> * Sending mail to the Working Group 2 mailing list <https://groups.google.com/g/scheme-reports-wg2> (you do not need a google account) * Sending mail to the Scheme Reports mailing list <https://scheme-reports.simplelists.com/> and <[email protected]> * Sending mail to the corresponding member Peter McGoron at <[email protected]>. I will forward your comment to the public issue tracker. Please indicate if you wish to be anonymous.

> The biggest new feature is the ability to mix definitions and expressions in bodies, such as the body of a lambda.

Looks like Rust. It helps macros a lot

Delimited continuation machinery? It seems like call/cc is becoming quite a bit more acknowledged as being overkill while the more restricted shift/reset, control/prompt, F-operator stuff, etc. compose better.

We plan to add delimited continuations in a later draft. What the actual API will look like is still in question. There is a proposal for a large API, like Racket's <https://srfi.schemers.org/srfi-226/> and a minimalistic API <https://srfi.schemers.org/srfi-248/> similar-ish to Guile's.

I hope you don't take this question the wrong way: why is R7RS large taking so long? Is there a consensus problem or just a lack of resources? If it's the latter, is there any way a random scheme dabbler can help?

The committee needs to think long and hard about which features to propose in each docket and what those features should look like, a lot of discussion needs to take place in order to get each docket formed, then the wider public needs to get its chance to weigh in, and then a voting round needs to be held. That process may need to happen several times for a docket, and there's a bunch of dockets planned before R7RSL will be done.

Think of it this way: if the committee was more cavalier about this we'd have the familiar situation where we start with a great language and then every update worsens it until we end up with an abominable horror show.

What tmtvl said is correct. However, it is also a resource problem. R7RS Large is a volunteer driven effort where if people stop having the time to contribute due to personal reasons, things slow down.

> If it's the latter, is there any way a random scheme dabbler can help?

Giving your comments on drafts, issues[1], and draft SRFIs is always welcome. The decisions of the Working Group are more complete when we hear more voices.

[1]: https://codeberg.org/scheme/r7rs/issues