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Date: Mon, 26 Apr 2021 22:18:32 +0300
From: "dmn (graahnul DOT grom AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
To: geda-user AT delorie DOT com
Subject: Re: readlink in guile (Re: [geda-user] system wide config)
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On Thu, 22 Apr 2021 14:33:23 +0200 (CEST)
"karl AT aspodata DOT se [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
wrote:

> Dmitry:
> > On Tue, 20 Apr 2021 16:46:34 +0200 (CEST)
> > "karl AT aspodata DOT se [via geda-user AT delorie DOT com]"
> > <geda-user AT delorie DOT com> wrote:
> ...
> > > (define (readlink file)
> > >   (let*
> > >    (
> > >     (port (open-input-pipe (string-append "readlink -f " file)))
> > >     (str  (read-line port))
> > >     (close-pipe port)
> > >    )
> > >    str
> > >   )
> > > )
> ...
> > Karl, first of all, I'd like to thank you for not using the "dog's
> > breakfast coding style" (TM)! :-)
> 
> What is that ?
> Is it about all thoose {str|d}angling parentheses...


Yes... But never mind, I'm just kidding.
I invented this term specifically to troll guile programmers. :-)
When I started learning the language, it was a nightmare
(just look at the "examples" in the guile reference manual).
Then I developed my own coding style, which reflects something
that human beings can read, understand, modify and refactor.
After that learning guile became no more difficult than
learning any other new language.
What it looks like you can see in one of the examples
I've written for lepton-schematic:
https://graahnul-grom.github.io/scm/select-locked.scm.html
(and in the Lepton EDA code, too :-) ).

> 
> > Being not an expert in the bloody lisp programming language, I
> > wonder does the call "(close-pipe port)" inside the "let" clause
> > get executed? (It looks like a variable definition).
> 
> No, you are right, but I can do it like this (it is nice to have
> open and close close to each other):
> 
> (define (readlink file)
>   (let*
>    (
>     (port (open-input-pipe (string-append "readlink -f " file)))
>     (str  (read-line port))
>     (dummy (close-pipe port))
>    )
>    str
>   )
> )
> 
> but perhaps it is better doing this like:
> 
> (define (read1pipe cmd)
>   (let*
>    (
>     (port (open-input-pipe cmd))
>     (str  (read-line port))
>    )
>    (close-pipe port)
>    str
>   )
> )

Yes, that's right.

> 
> (define (readlink file) (read1pipe (string-append "readlink -f "
> file)))
> 
> Regards,
> /Karl Hammar
> 


Regards,
Dmitry.

-- 
Lepton Electronic Design Automation
https://github.com/lepton-eda/lepton-eda
https://graahnul-grom.github.io