Re: [PATCH] add language/wisp to Guile?

[Dr. Arne Babenhauserheide]

Thank you for your review!

Maxime Devos <maximedevos@telenet.be> writes:

>> Why add Wisp?
>> For Wisp: it is then available directly wherever Guile is available.
>>           This will make it much easier for people to follow tutorials.
>
> I'm not convinced of this argument, because package managers exist, but ...
>
>> For Guile:
>> - Wisp has proven to be good at enabling people to get an
>>   entrance to Scheme² without pulling them out of the community.
>> - [...]
>
> ... all good points, and the implementation of Wisp is tiny anyway.
> For an additional reason: Wisp is a SRFI (Scheme Requests for
> Implementation) and Guile is a Scheme implementation.

That’s a good point — I should really have written it :-)

>> So I’d like to ask: can we merge Wisp as supported language into Guile?
>
> From some conversations elsewhere, I got the impression that
>
> (use-modules (foo))
>
> will search for foo.scm and not in foo.w.  I think you'll need to
> tweak the loading mechanism to also look for foo.w instead of only
> foo.scm, if not done already.

This needs an addition to the extensions via guile -x .w — I wrote that
in the documentation. I didn’t want to do that unconditionally, because
detecting a wisp file as scheme import would cause errors.

Is there a way to only extend the loading mechanism to detect .w when
language is changed to wisp?

readable uses

(set! %load-extensions (cons ".sscm" %load-extensions))

Would that be the correct way of doing this?

> Also, I think that when foo.go exists, but foo.scm doesn't, then Guile
> refuses to load foo.scm, though I'm less sure of that. If this is the
> case, I propose removing the requirement that the source code is
> available, or alternatively keep the 'source code available'
> requirement and also accept 'foo.w', if not done already.

I think accepting any extension supported by any language in Guile would
be better.

>> +; Set locale to something which supports unicode. Required to avoid
>> using fluids.
>> +(catch #t
>
>  * Why avoid fluids?

I’m not sure anymore. It has been years since I wrote that code …

I think it was because I did not understand what that would mean for the
program. And I actually still don’t know …

Hoow would I do that instead with fluids?

>  * Assuming for sake of argument that fluids are to be avoided,
>    what is the point of setting the locale to something supporting
>    Unicode?

I had problems with reading unicode symbols. Things like
define (Σ . args) : apply + args

> As-is, it now becomes impossible to use 'gettext' to translate
> software to non-English locales when the software imports (language
> wisp), which seems unfortunate to me.

That is very much not what I want.

> If you elaborate on what your
> goal here is, maybe I have an alternative solution.

This is to ensure that Wisp are always read as Unicode. Since it uses
regular (read) as part of parsing, it must affect (read), too.

>> +         ;; allow using "# foo" as #(foo).
>> +         (read-hash-extend #\# (λ (chr port) #\#))
>
> That's a rather Wisp-specific extension, but it appears you are
> extending things globally.  Instead, I propose extending it
> temporarily, with the undocumented '%read-hash-procedures' fluid.
>
>> +       (let
>> +         (
>> +           (l
>
> Lonely parenthesis.

Thank you! Will be fixed :-)

> +             (not (= 0 (line-real-indent (car lines ))))); -1 is a
> line with a comment
>
> Superfluous space after 'lines'.
>
>> +                             ; simple recursiive step to the next line
>
> I think the convention is ';;', OTOH there exist multiple conventions.
>
> +(define (wisp-scheme-replace-inline-colons lines)
> +         "Replace inline colons by opening parens which close at the
> end of the line"
>
> Too much space; convention is two spaces.

> (Similar styles issues in other places.)
> "guix style" might be useful.

I’ll do that …

>> +(define (wisp-replace-paren-quotation-repr code)
>> +         "Replace lists starting with a quotation symbol by
>> +         quoted lists."
>> +         (match code
>> +             (('REPR-QUOTE-e749c73d-c826-47e2-a798-c16c13cb89dd a ...)
>> +                (list 'quote (map wisp-replace-paren-quotation-repr a)))
>> [...]
>> +(define wisp-uuid "e749c73d-c826-47e2-a798-c16c13cb89dd")
>> +; define an intermediate dot replacement with UUID to avoid clashes.
>> +(define repr-dot ; .
>> +       (string->symbol (string-append "REPR-DOT-" wisp-uuid)))
>
> There is a risk of collision -- e.g., suppose that someone translates
> your implementation of Wisp into Wisp.  I imagine there might be a
> risk of misinterpreting the 'REPR-QUOTE-...' in
> wisp-replace-parent-quotation-repr, though I haven't tried it out.

This is actually auto-translated from wisp via wisp2lisp :-)

> As such, assuming this actually works, I propose using uninterned
> symbols instead, e.g.:
>
> (define repr-dot (make-symbol "REPR-DOT")).

That looks better — does uninterned symbol mean it can’t be
mis-interpreted?

Can I (match l ...) on uninterned symbols? They are used to match on
precisely these symbols later.

Can I write it into a string and then read it back?

When I see them, I have to turn them into a different representation
that I can then write back into the string and allow it to be read by
the normal reader.

> If this change is done, you might need to replace
>
> +             ;; literal array as start of a line: # (a b) c -> (#(a b) c)
> +             ((#\# a ...)
> +               (with-input-from-string ;; hack to defer to read
> +                   (string-append "#"
> +                       (with-output-to-string
> +                           (λ ()
> +                             (write (map
> wisp-replace-paren-quotation-repr a)
> +                                     (current-output-port)))))
> +                   read))
>
>
> (unverified -- I think removing this is unneeded but I don't
> understand this REPR-... stuff well enough).

The REPR supports the syntactic sugar like '(...) for (quote ...) by turning
(' ...) into '(...).

Also it is needed to turn ((. a b c)) into (a b c).

However the literal array is used to make it possible to define
procedure properties which need a literal array.

> Also, I wonder if you could just do something like
>
>   (apply vector (map wisp-replace-paren-quotation-repr a))
>
> instead of this 'hack to defer to read' thing.  This seems simpler to
> me and equivalent.

That looks much cleaner. Thank you!

> (AFAIK, these REPR-... symbols are never written to a port or turned
> into syntax, so I think that uninterned symbols would work here.)

They are unread into a string.

> (Aside from the REPR-... thing, I'm assuming (language wisp) is
> alright -- the SRFI is in 'final' status and it has been stable for
> years now, after all.)

Thank you!

Best wishes,
Arne
-- 
Unpolitisch sein
heißt politisch sein,
ohne es zu merken.
draketo.de

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