Re: How to select git:send-email output in config.scm?

[EuAndreh <eu@euandre.org>]

Tobias Geerinckx-Rice <me@tobias.gr> writes:

> Indeed, my first mail was too hurried & my longer mail didn't 
> address this part at all...
>
>   (packages
>     (append
>       (list (list git "send-email")
>             (list git "gui")            ; just another example
>             foo
>             ...)
>       (map specification->package
>            '("git"
>              "bar"
>              ...)
>
> PACKAGES takes a list of, well, packages -- *or* (package output) 
> sublists!  This is not well-documented: it's mentioned in 
> gnu/system.scm, but not in the manual under ‘operating-system 
> Reference’.  I will add it there.  Thank you for pointing it out.

Thanks for the explanation, now I could make it work.

> If you want to go one step further, get rid of APPEND, and MAP 
> everything: it's not hard to write a procedure similar to 
> specification->package+output that returns a list instead of 
> multiple values (hint: take a look at DEFINE-VALUES).  There might 
> well already be one hiding somewhere.  I don't know.
>
> For today, at least, I'll leave this as an excercise for the 
> reader.  :-p

Challenge accepted! :)

I was able to put handle both cases with a single function. I wasn't
able to get rid of map, though. Here's what I got so far:

--8<---------------cut here---------------start------------->8---
(use-modules (gnu)
             (srfi srfi-1))

(operating-system
  (packages
    (append
     (map (lambda (spec)
            (if (not (string-contains spec ":"))
                (specification->package spec)
                (let ((spec-pair (string-split spec #\:)))
                  (list (specification->package (first spec-pair))
                        (second spec-pair)))))
          '("git"
            "git:send-email"))
     %base-packages))
  ...))
--8<---------------cut here---------------end--------------->8---

Any suggestions?