From: "Linus Björnstam" <linus.bjornstam@veryfast.biz>
To: "Stefan Israelsson Tampe" <stefan.itampe@gmail.com>,
guile-devel <guile-devel@gnu.org>
Subject: Re: Fwd: Announcing the first stable release of guile-for-loops
Date: Fri, 24 Jan 2020 22:23:43 +0100 [thread overview]
Message-ID: <9d853449-2dbd-49ae-b17c-15fa592d4cc0@www.fastmail.com> (raw)
In-Reply-To: <CAGua6m1D8n2jW62a=L_qE9RSoxaj3t=jRuK_vtKkwA2X2TqZcw@mail.gmail.com>
Yeah, when iterating through many different things at the same time it is extremely helpful.
I would have loved syntax parse when writing the macros :) I read your for loops code in awe, at least until I saw how you "cheated" with set! :-P
My only chance of getting it into guile proper would be to 1. Make a SRFI and survive the SRFI process with my honour intact and 2. Code cleanup. Most of for/emit is OKish, but for/foldr needs to be beaten with a stick, burnt and rewritten. "bending hygiene" doesn't quite cover what I did to make it work. In the end I sort of kind of worked around it by making an API change, but it still stinks. Defining a new loop using for/foldr involves having to do a syntax->datum->syntax. No fun. I could check how racket does it, but given they can do syntax-local-introduce (which is specific to their "hygiene as sets of scopes") I suspect I am out of luck.
Väl mött
Linus Björnstam
On Fri, 24 Jan 2020, at 13:13, Stefan Israelsson Tampe wrote:
>
>
> ---------- Forwarded message ---------
> From: *Stefan Israelsson Tampe* <stefan.itampe@gmail.com>
> Date: Fri, Jan 24, 2020 at 12:42 PM
> Subject: Re: Announcing the first stable release of guile-for-loops
> To: Linus Björnstam <linus.bjornstam@veryfast.biz>
>
>
> Would be cool to have those implemented in guile, that would make my
> guile-syntax-parse a bit leaner
>
> Regards
> Stefan
>
> On Thu, Jan 23, 2020 at 3:03 PM Linus Björnstam
> <linus.bjornstam@veryfast.biz> wrote:
> > Hiya everybody!
> >
> > I have spent some time implementing efficient for loops for guile, and they are baked and ready to go. I have worked the last weeks at implementing generalized support for non-tail-recursive loops and am happy to announce for/foldr. It is a generic right fold, with support for delaying it's arguments as either thunks or promises.
> >
> > The syntax is more or less the same as racket's loops, and they are generally compatible. The code generated is for almost all cases as fast as hand-rolled code. They are all expressed as left or right folds, and are as such (apart from for/list, but read about that in the documentation) free of mutation. They are all converted to named lets.
> >
> > Some examples:
> >
> > (for/list ((a (in-range 1 6)))
> > (* a a)) ;; => (1 4 9 16 25)
> >
> > (for*/list ((a (in-string "ab")) (b (in-range 1 3)))
> > (list a b))
> > ;; => ((#\a 1) (#\a 2) (#\b 1) (#\b 2))
> >
> > There are many more looping constructs, among others:
> > for/sum, for/vector, for/or, for/and, for/first, for/last and a side-effecting simple for.
> >
> > Here is a sieve of erathostenes:
> >
> > (define (erathostenes n)
> > (define vec (make-vector n #t))
> > (for/list ([i (in-range 2 n)] #:when (vector-ref vec i))
> > (for ([j (in-range/incr (* 2 i) n i)])
> > (vector-set! vec j #f))
> > i))
> >
> > The code and documentation is available here:
> > https://hg.sr.ht/~bjoli/guile-for-loops
> >
> > A web-friendly documentation can be found here:
> > https://man.sr.ht/%7Ebjoli/for-loops-docs/for-loops.md <https://man.sr.ht/~bjoli/for-loops-docs/for-loops.md>
> >
> > The thing I had been waiting for is right fold. That allows us to write loops like guile's map: non-tail recursive:
> > (for/foldr ((identity '())) ((a (in-list '(1 2 3))))
> > (cons (* a a) identity))
> >
> > becomes equivalent to:
> >
> > (let loop ((random-identifier '(1 2 3)))
> > (if (null? random-identifier)
> > '()
> > (let ((a (car random-identifier)))
> > (cons (* a a) (loop (cdr random-identifier))))))
> >
> > Happy hacking
> > Linus Björnstam
> >
prev parent reply other threads:[~2020-01-24 21:23 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-23 12:03 Announcing the first stable release of guile-for-loops Linus Björnstam
[not found] ` <CAGua6m3=DU=G3jkPqMxX5Bw6r4p394Uh3fV6KeUbrf-_iqxAeQ@mail.gmail.com>
2020-01-24 12:13 ` Fwd: " Stefan Israelsson Tampe
2020-01-24 18:26 ` Nala Ginrut
2020-01-24 21:23 ` Linus Björnstam [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: https://www.gnu.org/software/guile/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=9d853449-2dbd-49ae-b17c-15fa592d4cc0@www.fastmail.com \
--to=linus.bjornstam@veryfast.biz \
--cc=guile-devel@gnu.org \
--cc=stefan.itampe@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).