Re: [Flightgear-devel] Radio frequency range: min/max/wrap

[Julian Foad]

Norman Vine wrote:

Julian Foad writes:

Norman Vine wrote:

A proper version needs to be based on Interval Arithmetic we could just snag a subset of the scalar functions from an existing package http://www.ti3.tu-harburg.de/~knueppel/profil/docu/Profil.texinfo_19.html

Er ... we are not trying to do arithmetic on intervals. We are just incrementing and decrementing a scaler value within an interval.

Er... If you want to assign a 'stepsize' that is not an integral value then you are doing Interval Arirthmetic

Do you mean in the sense of using a tiny interval like [0.0999999,0.1000001] to represent a value like 0.1 that cannot be represented exactly in binary? I don't see how this would be particularly useful.

also note I said 'snag a subset' ie just the scalar add and subtract parts

Like this one?
INTERVAL AddBounds (REAL r, REAL s)
Returns an interval containing an enclosure of the true sum of r and s.

So when advancing past the last valid frequency we could have AddBounds(135.975, 0.025) and it returns an interval that encloses 136.0 (presumably the smallest such interval). Then what?

Could you give an example of what you mean? I don't follow.

Granted you can make a special arithmetic for the frequency adjuster
but why not use a proven mathematically sound methodology that will just work for any stepsize for all adjusters with or without wrap around

I am explicitly aiming for a general implementation, not just for the radio frequencies.

Take a look at the patch I just submitted and let me know if you think it's OK.

- Julian


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