kicad-developers team mailing list archive

[Jon Evans <jon@xxxxxxxxxxxxx>]

Why is B safer? To me, B sounds riskier as there is a chance we are
throwing away data. I'm not in favor of implementing B without a clear spec
(and I guess Ucamco would need to be involved) on what guarantees can be
made.

Right now, we implement B based on some apparently arbitrary assumptions
about what data can be thrown away. Re-implementing the current behavior in
the new library would certainly be possible, I'm just not convinced that
it's the best plan.

-Jon

On Tue, Dec 24, 2019, 13:54 Jeff Young <jeff@xxxxxxxxx> wrote:

> Safest would be (b).
>
> We could probably do something pretty dumb (ie: set a single value in the
> JSON printer which it uses for precision).
>
> On 24 Dec 2019, at 15:22, Jon Evans <jon@xxxxxxxxxxxxx> wrote:
>
> Hi all,
>
> The Gerber job file specification[1] says that the format follows the JSON
> standard, and doesn't say much else about numeric value storage.
>
> But, in the examples in that spec, decimal (floating-point) values are all
> truncated with only a few digits after the decimal point.
>
> The manual JSON generation code that exists today follows along these
> examples, truncating floating-point numbers using formatting like %.3f and
> so on.  Now I'm working on switching us over to using a library for this
> JSON generation, but it will output floating-point values as doubles
> without any such truncation.
>
> For computer software reading these job files, I would guess this has no
> impact.  But for humans opening up the file, they may find that the numbers
> stored don't match their expectations.
>
> What should we do about this?
> (a) nothing, storing doubles in the file is fine
> (b) find some way to manually truncate/round values to some precision, but
> still write them to the file as "decimals" -- if so, what should the spec
> be for this rounding / truncation?
> (c) something else?
>
> Best,
> Jon
>
> [1]
> https://www.ucamco.com/files/downloads/file/209/the_gerber_job_format_specification.pdf
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