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Date: Sat, 12 Sep 2015 17:37:46 +0200 (CEST)
From: Roland Lutz <rlutz AT hedmen DOT org>
To: "Vladimir Zhbanov (vzhbanov AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
Subject: Re: [geda-user] About reinventing the wheel, and how to avoid it
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On Sat, 12 Sep 2015, Vladimir Zhbanov (vzhbanov AT gmail DOT com) [via geda-user AT delorie DOT com] wrote:
> On Fri, Sep 11, 2015 at 04:06:36PM +0200, Roland Lutz wrote:
>> [C code]
>
> And that's an impenetrable code for the same in Guile:
>
>  (use-modules (geda page))
>
>  ; Checks if the OBJECT is a circle or an arc with zero radius
>  (define (zero-radius-object? object)
>    (or
>      (and (circle? object) (= (circle-radius object) 0))
>      (and (arc?    object) (= (arc-radius    object) 0))))
>
>  (apply page-remove! (active-page)
>         (filter
>           zero-radius-object?
>           (page-contents (active-page))))

Or, assuming a similar syntax that preserves the information needed to 
optimize the request:

     (delete-selected-objects! (active-page)
                               (select-by-radius (active-page) 0))

> Just about reinvention of the wheel. :-/

The point here isn't C vs. Scheme.  The point is iterating over all 
objects vs. passing a structured request to the library.  My example is in 
C because the libxornstorage interface is in C, and that's because it's 
generally a good idea to have a library interface in C unless there is 
good reason to do otherwise.

I don't seriously expect anyone (except maybe hardcore C fans) to use the 
C interface directly (though I tried hard to make it as well-usable as 
possible).  I'm not even using it directly myself except for the test 
cases.  The intended use case is to write language bindings for some 
high-level language--in my case, it was Python, it may be Scheme for 
you--and use that language from then on.