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From: Taylan Kammer <taylan.kammer@gmail.com>
To: raid5atemyhomework <raid5atemyhomework@protonmail.com>,
	"guix-devel@gnu.org" <guix-devel@gnu.org>
Subject: Re: A new paradigm for modifying operating system declarations
Date: Mon, 4 Jan 2021 21:21:20 +0100	[thread overview]
Message-ID: <87b59430-b53e-47ec-32d5-abbd3be42ce7@gmail.com> (raw)
In-Reply-To: <ewUh5vMEW_m5K1m9xYSvxi0_o92wTXSO8pAoyBec8LDT45bZmrNXc6hPH4_3ZXWTyqe91NDltmJgH5mEDbpsu-A6Ar0vpDqky8F4kCrhlcI=@protonmail.com>

On 04.01.2021 16:38, raid5atemyhomework wrote:
> Hi guix-developers,
> 
> I'd like to propose an idea for constructing `<operating-system>` objects.
> 
> [... snip ...]
> 
> What are your opinions?  Blech?  Yummy?  Is it worth exploring this paradigm for adding particularly complex features to an operating system definition?

Hi,

Interesting idea.

First, let me point out a more conventional alternative to what your 
'decorate' macro does:

   (define (compose proc . rest)
     "Functional composition; e.g. ((compose x y) a) = (x (y a))."
     (if (null? rest)
         proc
         (let ((rest-proc (apply compose rest)))
           (lambda x
             (let-values ((x (apply rest-proc x)))
               (apply proc x))))))

This allows for something like:

   ((compose install-foo install-bar install-zfs)
    (operating-system ...))

Or perhaps cleaner:

   (define my-os-modifier (compose install-foo install-bar install-zfs))

   (my-os-modifier
    (operating-system ...))

If you need custom modifications within, you can do:

   (define my-os-modifier
     (compose install-foo
              (lambda (os) ...)
              install-bar))

It's more verbose, but doesn't "break" standard Scheme syntax as much. 
Function composition is conceptually pretty easy and probably more 
well-known than "decorators" (which I had never heard of, personally).

Fewer macros means the reader needs to keep fewer special rules in mind.

---

Secondly, I wonder if passing an OS declaration through various 
procedures that modify it is really the best approach in the first place.

For build phases, we have the 'modify-phases' syntax.  For services, 
there is 'modify-services'.  Maybe there should be a 'modify-os' kind of 
syntax.  (In other words, if we're going to invent new syntax, why not 
go all-out and create the most convenient syntax for the use-case.)

Just my thoughts.


- Taylan


  reply	other threads:[~2021-01-04 20:23 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-04 15:38 A new paradigm for modifying operating system declarations raid5atemyhomework
2021-01-04 20:21 ` Taylan Kammer [this message]
2021-01-05  0:32   ` raid5atemyhomework
2021-01-05  6:12     ` Carlo Zancanaro
2021-01-05 10:01       ` raid5atemyhomework
2021-01-04 23:26 ` Jan Wielkiewicz
2021-01-05  0:46   ` raid5atemyhomework

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