Good evening,

EuAndreh 写道：
>> Use specification->package+output.
>
> I tried that, and it indeed doesn't complains about 'unknown 
> package'
> anymore. However, send-email is still not installed after a 
> system
> reconfigure:

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.

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

Kind regards,

T G-R