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From:	geda AT psjt DOT org (Stephan =?utf-8?Q?B=C3=B6ttcher?=)
To:	"Britton Kerin \(britton.kerin\@gmail.com\) \[via geda-user\@delorie.com\]" <geda-user AT delorie DOT com>
Subject:	Re: [geda-user] The nature of gEDA users
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Date:	Wed, 27 Jan 2016 08:40:00 +0100
In-Reply-To:	<CAC4O8c9RDJc17XGo-H6DuN5h76RKhQmRNGpcn3DKBKUBP=PuCg@mail.gmail.com>
	(Britton Kerin's message of "Tue, 26 Jan 2016 13:35:50 -0900")
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"Britton Kerin (britton DOT kerin AT gmail DOT com) [via geda-user AT delorie DOT com]"
<geda-user AT delorie DOT com> writes:

> On Tue, Jan 26, 2016 at 12:19 PM, John Doty <jpd AT noqsi DOT com> wrote:
>>
>> On Jan 26, 2016, at 2:02 PM, Stephan Böttcher <geda AT psjt DOT org> wrote:
>>
>>> But the first steps should not be "implement b/b vias" or "allow more
>>> than one pair of outer layers".  It should be something like "expess
>>> Elements and Vias as subclasses of generic containers that can include
>>> anything".
>>
>> +1
>
> So you guys actually want a more strongly typed system.  

No.

The Via is a container with Attribute "Via".  An Element is a container
with Attibute "Element".  The GUI HID shall present those as special
types to the user, in component libraries and via stack editors. But in
the data structures those could well the the same as a hierachical
sublayout.

> That's pretty different from gschem, which uses attributes (duck
> types) for most things.

I like attributes.

> Regarding making arbitrary containers, I'm not convinced its a good
> idea.  Entire layouts serve much the same purpose and can easily be
> copied about. 

I'd like to instanciate the same sublayout by reference, so I can edit
the master and all copies follow.  Problem: How to override atributes
(refdes) on the copies?

> Admittedly I'm not convinced the other way either, since I generally
> prefer types to attributes.  However, there's no denying attributes
> are easier and can be added incrementally.  Type hierarchies have the
> further disadvantage of being closed to user extension in C (and
> effectively so in most other languages as well).

Types require that you know all use cases beforehand.

How about implementing types in HID code on top of the attribute driven
data structures?


Container{
  Attributes{
        type="Via",
        origin=(1003mil,234mil),
        }
  Circle{layer="microvias-top", radius=20mil, center=(0,0)},
  Circle{layer="component", depth=20, radius=40mil, center=(0,0)},
  Circle{layer="ground", depth=20, radius=40mil, center=(0,0)},
  Circle{layer="component", depth=-35, radius=50mil, center=(0,0),
         Attributes{thermal="clerance"},
  Circle{layer="ground", depth=-35, radius=50mil, center=(0,0),
         Attributes{polarity="neg",
                    thermal="clerance"},
  Line{layer="ground", depth=34, ...
       Attributes{thermal="diagonal,square"}
      }
  }

The thermal tool knows about this type="Via" and is allows to delete/add
objects with attribute "thermal".


-- 
Stephan

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