Subject: Re: [PATCH v2 1/3] gnu: racket: Update to 8.2.

From: Philip McGrath <[email-masked]>
Date: Sun, 25 Jul 2021 14:04:35 -0400

Hi,

On 7/25/21 9:03 AM, Leo Prikler wrote:
>> On 7/19/21 2:31 AM, Philip McGrath wrote:
>>> +         (add-before 'configure 'initialize-config.rktd
>>>               (lambda* (#:key inputs #:allow-other-keys)
>>> -             (chdir "src")
>>> +             (define (write-racket-hash alist)
>>> +               ;; inside must use dotted pair notation
>>> +               (display "#hash(")
>>> +               (for-each (match-lambda
>>> +                           ((k . v)
>>> +                            (format #t "(~s . ~s)" k v)))
>>> +                         alist)
>>> +               (display ")\n"))
>>> +             (mkdir-p "racket/etc")
>>> +             (with-output-to-file "racket/etc/config.rktd"
>>> +               (lambda ()
>>> +                 (write-racket-hash
>>> +                  `((lib-search-dirs
>>> +                     . (#f ,@(map (lambda (lib)
>>> +                                    (string-append (assoc-ref
>>> inputs
>> lib)
>>> +                                                   "/lib"))
>>> +                                  '("openssl"
>>> +                                    "sqlite"))))
>>> +                    (catalogs
>>> +                     . (,(string-append
>>> +                          "
>>> https://download.racket-lang.org/releases/"
>>> +                          ,version
>>> +                          "/catalog/")
>>> +                        #f))))))
>>>                 #t))
> This is perhaps a somewhat noobish question, but why must we use dotted
> pair notation here?  To me personally, reading '(a . (b c)) is
> confusing as it could more clearly be written as '(a b c).  Is this a
> Racket convention?

Yes, the Racket reader requires that hash table literals use dotted pair 
notation, e.g. #hash((a . (b c))(d . 2)). (Additionally, hand-written 
Racket would often use square brackets for the key–value pairs.) I think 
it's ultimately for historical reasons, but there are various 
subtleties: under `quasiquote`, for example, the value position can 
contain `unquote`, but the key position cannot.

Of course, that doesn't necessarily mean the Guile code must use dotted 
pairs, but, at least as a Racketeer, I found writing these s-expressions 
with a bit of a "Racket accent" helped me to remember that this code is 
generating Racket.

> To attempt a better summary: Specifying `#f' will allow Racket to
> search for user-specific libraries etc. (in
> $XDG_DATA_HOME/racket/$RACKET_VERSION) in addition to "system-specific"
> libraries stored in $HOME/.guix-profile, am I correct?
> 
> If so, then yes, doing that is absolutely fine (you could compare it to
> how Emacs users can still install stuff via ELPA).

Yes, that's a much better summary.

(Pedantically, the user-specific path could be different, depending on 
the configured installation name and other things.)

The other issue is that I believe *not* specifying `#f` for 
`racket-minimal` would break the build of `racket` starting in the 
second patch, when the main distribution becomes a layer chaining to 
`racket-minimal`. At least, it broke some examples of layered 
installation I tried, which is how I figured out I'd done the wrong 
thing in <https://issues.guix.gnu.org/47180>. If that were the only 
issue, there might be some other workaround, but it's worth bearing in 
mind, particularly because the problems caused by buggy "config.rktd" 
files can be subtle and easy to miss.

-Philip