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From: ludo@gnu.org (Ludovic Courtès)
To: Hartmut Goebel <h.goebel@crazy-compilers.com>
Cc: help-guix@gnu.org
Subject: Re: string-append plus package
Date: Sat, 31 Dec 2016 00:42:37 +0100	[thread overview]
Message-ID: <87wpeh6l1u.fsf@gnu.org> (raw)
In-Reply-To: <3f930a82-663f-17ed-466c-d3bd021023d8@crazy-compilers.com> (Hartmut Goebel's message of "Thu, 29 Dec 2016 11:57:16 +0100")

Hey Hartmut,

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

> Am 19.12.2016 um 10:47 schrieb Ludovic Courtès:
>> Hartmut Goebel <h.goebel@crazy-compilers.com> skribis:
>>
>>> Am 08.12.2016 um 20:56 schrieb Leo Famulari:
>>>>> Here is the service-definition I use:
>>>>>
>>>>>              (nginx-service #:vhost-list
>>>>>                (list (nginx-vhost-configuration     
>>>>>                       (root (string-append nginx "/share/nginx/html"))
>>>> I believe that file-append is intended for this use case.
>>> Maybe, but I can't get it to work. This minimal system declarision fails
>>> with "In procedure string-append: Wrong type (expecting string):
>>> #<<file-append> base: #<package nginx@1.11.6 gnu/packages/web.scm:126
>>> 2a236c0> suffix: ("/")>"
>>>
>>> (use-modules (gnu))
>>> (use-package-modules networking web)
>>> (define NGINX (file-append nginx "/bin/nginxctl"))
>>> (define TEST (string-append NGINX ""))
>> […]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")
>>
>> HTH!
>
> I now found time trying this out. Unfortunately this does not do what I
> expect. I do not need some string "(foo bar
> \"/gnu/store/…-nginx-1.2.3/foo/bar\")".
>
> I need the string "/gnu/store/…-nginx-1.2.3/bin/nginxctl". No gexpr, no
> scheme magic, no string representing scheme code. But simply a string
> containing the path of a file with the package (nginx in the example)
> which I can assign to some variable (NGINX as shown in the example) and
> then be used for other string operations (like when defining TEST in the
> example).
>
> I tried adopting your example but #~ always gave me a gexp, which of
> course I can't use in string-append.
>
> The manual says "Gexps are meant to be written to a file …" so I assume
> "file-append" is the wrong approach at all

Where does that string you want to build go to?

Depending on the answer, the solution would be either a gexp with
‘file-append’ or the solution that Mathieu outlined with
‘package-output’ (the latter looks simpler but is also more “risky” in
that that you could end up with strings that refer to nonexistent store
items.)

Ludo’.

  parent reply	other threads:[~2016-12-30 23:42 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-08 17:01 string-append plus package Hartmut Goebel
2016-12-08 17:28 ` Thompson, David
2016-12-08 17:46   ` Hartmut Goebel
2016-12-08 17:47     ` Thompson, David
2016-12-08 19:56 ` Leo Famulari
2016-12-19  0:13   ` Hartmut Goebel
2016-12-19  9:47     ` Ludovic Courtès
2016-12-19 11:05       ` Hartmut Goebel
2016-12-19 13:31         ` Ludovic Courtès
2017-01-01 15:34           ` Hartmut Goebel
2017-01-02 23:05             ` Ludovic Courtès
2016-12-29 10:57       ` Hartmut Goebel
2016-12-29 13:06         ` Mathieu Lirzin
2016-12-29 14:21           ` Hartmut Goebel
2016-12-30 23:42         ` Ludovic Courtès [this message]
2016-12-31 12:56           ` Hartmut Goebel
2017-01-02 23:10             ` Ludovic Courtès

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