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Subject: Re: [geda-user] The nature of gEDA layers
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From: John Doty <jpd AT noqsi DOT com>
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Date: Sat, 30 Jan 2016 09:48:55 -0700
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On Jan 30, 2016, at 9:03 AM, DJ Delorie <dj AT delorie DOT com> wrote:

> Despite some folks dreams to the contrary, a layout program is not a
> generic CAD program.

Whose dreams?

>  It has to have *some* understanding of what the
> layout *means* in order to be useful to the designer.  Otherwise you
> might as well use a paint program.

Nobody has ever asserted otherwise on this group. The assertion is that =
putting a layout program on a solid physical foundation make it easier =
for the designer to understand and to construct what the job needs. A =
paint program lacks that foundation. But so does pcb.

The fact that gschem is essentially a generic topology editor is a =
strength. The designer can build arbitrarily complicated structures atop =
that foundation. Again, a paint program would not suffice, but a program =
that restricted the user to a particular model of circuit design would =
not suffice either. We see the consequences of a particular model in =
drc2, which complains vehemently about all kinds of things that aren=92t =
problems, but don=92t fit its model. But, since drc2 is not part of =
gschem, its difficulties cause little harm. Hurray for separation of =
concerns!

Your sin() function in your favorite programming language does not =
understand that its argument is an angle. I suppose you=92d think this a =
problem. In fact, many applications (like Fourier analysis) depend on =
taking the sin() of variables that do not represent angles. Again, it is =
constructive to have a tool that has only a minimum of understanding and =
let the user provide that knowledge.

John Doty              Noqsi Aerospace, Ltd.
http://www.noqsi.com/
jpd AT noqsi DOT com



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