Subject:
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Re: Some comments on LPub
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Newsgroups:
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lugnet.cad
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Date:
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Sat, 26 Mar 2005 16:39:03 GMT
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Viewed:
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999 times
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In lugnet.cad, Kevin L. Clague wrote:
> In lugnet.cad, Anders Isaksson wrote:
> > Kevin L. Clague wrote:
> > > > a) For instance, when "l3p_use_seam_width true 0.800000" is in
> > > > the config file, then after loading, the seam value appears in LPub
> > > > as 0.800000011920929.
> > > > [...]
> > > > "color_scaling 0.650000 ..." in the config file, it is shown as
> > > > 36/64% in L3Pub after loading that config, and after saving it, it
> > > > is "color_scaling 0.640000 ..." in the config file. Subsequent
> > > > "0.996094 0.996094 0.996094".
> > >
> > > I will study this problem. I'm sure that I am just using
> > > sprintf("%f"), and sscanf("%f"), so I'm not sure what to do here.
> > > Anyone out there got ideas on this?
> >
> > This is exactly what happens when you read string numbers into a float (or
> > Pascal single) and then convert it to a double (or extended). Floating point
> > numbers are never exact in computers, and storing them with limited
> > precision (sprintf("%f")) will not make the situation better.
>
> Anders,
> Thanks very much. I'll see what I can do.
> Kevin
One way to adress this is to keep the setting in memory also as a string, and
never convert on the way of loading a config file into memory and saving it to a
file again. Only when the setting is used to do calculations, it is converted
from the internal string variable to a float or double variable, but it is never
converted back. This guarantees that it does not "move" between load/save
cycles, but the price is you have two internal variables instead of just one.
Andy
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