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Re: Scheme+

From: Linus Björnstam
Subject: Re: Scheme+
Date: Mon, 20 Dec 2021 09:15:49 +0100
User-agent: Cyrus-JMAP/3.5.0-alpha0-4524-g5e5d2efdba-fm-20211214.001-g5e5d2efd

Hi Damien!

I played around with it and it seems to rely heavily on mutation, which makes 
guile (and chez and racket for that matter) box the values. That adds a layer 
of indirection to memory access, meaning slower code (apart from the more 
obvious problems of continuation safety and threading safety). It could be 
partially fixed with a very much not fun to write syntax case macro: you expand 
a body as far as possible into a letrec* (and letrec-syntax) shadowing bindings 
when needed and use set! only in places where bindings are not declared. 

The workhorse you need for that is syntax-local-binding.

 If you want this system to be resilient and work well with other scheme code 
that is probably the path to go. One could imagining having a procedure form 
that is fully expanded, analyzed and then some-kind-of-CPS-transformed so that 
all variables are passed as state. That way you would get continuation and 
thread safety, while allowing something that seems like and, at least locally, 
behaves like mutation to take place. 

This (the local mutation part) is tangential to something I have wanted to 
write for a long time, but I have not had the time (nor intelligence). If you 
want to discuss some ideas or have any question we can take this off-list.

Another thing would be to not use call/cc in the def form. Let/ec is a lot 

  Linus Björnstam

On Mon, 20 Dec 2021, at 01:05, Damien Mattei wrote:
> Hi,
> I finished today the first version of Scheme+.
> Scheme+ is an extension of the syntax of the Scheme language.
> Scheme+ makes it easy the assignment of Scheme objects in infix (works also
> in prefix) notation with a few new operators  ← (or  <-), [ ],⥆ (or <+) .
> Scheme+ does much more things,see:
> or:
> static light HTML page:
> direct link to code and README:
> Best regards,
> Damien Mattei

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