Re: gEDA-user: pcb crooked traces

[Armin Faltl <armin.faltl@xxxxxx>]

Rick Collins wrote:
> Yes, it is about tolerance... and error.  How much error will be 
> introduced into a design if the system rounds all metric measurements 
> to 0.01 mils?  How much tolerance is acceptable?   When you can answer 
> these two questions for all designs and all users you can't expect 
> anyone to believe this is "nonsense"!  If you have a connector, for 
> example, with 100 pins spaced on metric centers, the accumulated error 
> can approach a half mil or 0.0127 mm.  That may be a significant 
> fraction of the pin spacing and likely not a good idea.  Larger 
> connectors would have more accumulated error.
While accumulation of error is an issue with floating point, the 
connector or any predefined
shape is a particularely bad example:
At least I wouln't convert the spacing and then sum up the erratic value 
but convert
all the original values, which gives exactly 1 conversion error per 
position, irrespective
of the number of pins/position. And that's exactly how the read routines 
operate.
To do it the wrong way, they would need to be fortune tellers, because 
there is
no 'array' element in new-lib files.


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