Re: string-append plus package

[ludo@gnu.org (Ludovic Courtès)]

Hartmut Goebel <h.goebel@crazy-compilers.com> skribis:

> Am 19.12.2016 um 10:47 schrieb Ludovic Courtès:
>> The result of ‘file-append’ is not a string, but ‘string-append’ expects
>> two strings, hence the error.
>>
>> ‘file-append’ returns a “string-valued gexp”.  This is to say that, in a
>> staging context, it will produce a string.  For example:
>>
>>   (scheme-file "foo" #~(foo bar #$(file-append nginx "/foo/bar")))
>>
>> leads to a file “foo” containing:
>>
>>   (foo bar "/gnu/store/…-nginx-1.2.3/foo/bar")
>
> Thanks for the explanation (which to be frank would take me some time to
> understand).
>
> Please reread you answer from the point of view of an administrator or
> somebody else who is not a Scheme programmer. Somebody who just wants to
> get some system up an running. He would answer like this:
>
>     Parton? What? "string-valued gexp", "staging context"? I do not
>     care. I simply want to get the path to a file within a package.
>
> Whatever you write above may be correct and may be understandable for
> every Scheme programmer. But this is discouraging for everybody who does
> not want to become a Scheme expert for administering his/her systems.
>
> I already wasted about an hour just to try to get this path! This is crap!

I agree!  The first two lines were all you wanted to know; the rest was
for you as someone who contributes to Scheme—I would not give that
explanation to someone who’s just trying to get nginx up and running.

As for the specifics of why ‘nginx-configuration’ makes this use case
complicated, I think we discussed it on guix-devel before, and there was
probably an action item, but “someone” just needs to make it happen or
at least to keep track of it.

HTH!  :-)

Ludo’.