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
