ludo@gnu.org (Ludovic Courtès) writes:

> Hello,
>
> Zachary Kanfer <zkanfer@gmail.com> skribis:
>
>> Running `guix package -m` on a file with this line `(list icedtea-2.6
>> "jdk")` gives an error "In procedure module-lookup: Unbound variable:
>> icedtea-2.6".
>>
>> I get the same error for the following lines:
>>
>> `(list icedtea-2.6.6 "jdk")`
>> `(list icedtea@2.6.6 "jdk")`
>>
>> `guix package -s icedtea` reports that there is a version 2.6.6. How do I
>> specify this in a manifest file? Thanks.
>
> You should use ‘specification->package’ as discussed at
> <https://www.gnu.org/software/guix/manual/html_node/Using-the-Configuration-System.html#index-specification_002d_003epackage>.
>
> The ‘specification->package’ procedure takes a spec like those you’d
> write on the ‘guix package -i’ command line, and returns the
> corresponding package.  ‘specification->package+output’ works similarly
> but also returns the specified output (the part that comes after the
> colon).
>
> So your manifest would look something like:
>
>   (use-modules (gnu))
>
>   (packages->manifest
>    (map (compose list specification->package+output)
>         '("icedtea@2.6.6:jdk" "emacs" "vim" …)))
>
> HTH!
>
> Ludo’.

Just for fun, I tried running some commands in a REPL.  I wanted to find
out why the "list" procedure was being used here.  What I saw was this:

--8<---------------cut here---------------start------------->8---
scheme@(guile-user)> (specification->package+output "icedtea@2.6.9:jdk")
$6 = #<package icedtea@2.6.9 gnu/packages/java.scm:347 39a6000>
$7 = "jdk"
scheme@(guile-user)> (list (specification->package+output "icedtea@2.6.9:jdk"))
$8 = (#<package icedtea@2.6.9 gnu/packages/java.scm:347 39a6000>)
scheme@(guile-user)> (map (compose list specification->package+output) '("icedtea@2.6.9:jdk"))
$9 = ((#<package icedtea@2.6.9 gnu/packages/java.scm:347 39a6000> "jdk"))
scheme@(guile-user)>
--8<---------------cut here---------------end--------------->8---

Why does the string "jdk" appear in $9 but not in $8?  It looks like the
list procedure ignored the second value (the "jdk" string) when
producing $8, but not when producing $9.  Is that true?  Why?

-- 
Chris