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Date: Wed, 26 Aug 2015 14:03:26 -0400
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From: DJ Delorie <dj AT delorie DOT com>
To: geda-user AT delorie DOT com
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Subject: Re: [geda-user] pcb file format
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> Exactly. PCB currently does this only it does not have all the
> information in a unified structure.

It's in 'extern PCBType *PCB;' so while the structure may be a little
obtuse, it's certainly unified.

> It does iterate through the list of connected items and build a
> netlist but things like design rules are apparently processed in a
> messier way.

Because the concept of "connected" in pcb becomes a geometry problem,
not a logic problem.  DRC is messy because it's a messy problem to
solve, with many solutions, and the one originally chosen wasn't
neccessarily the one we might have chosen today.

(btw: drc is handled by running the netlist code multiple times, so
that "but" doesn't work that way either - it's the *same* code ;)