Angles (Radians/Degrees) about dimensioned HOT 10 CLOSED

Radians should be dimensionless, which is likely to cause trouble with tracking them in terms of units.

from dimensioned.

Is there a problem with doing something like this?

make_units! {
    Angles, Unitless, one;
    base {
        Degree, degree, °;
    }
}

Then you have degrees and can use Unitless for radians. Using the SI system with 1 radian = m * m^-1 gives you the same thing for radians.

You can also add on any other units you would like to use.

from dimensioned.

Oh cool. I'll start working on the library now if that's ok.

What does Unitless do?

from dimensioned.

It's the type for something with no units. Say you run

make_units! {
    MS, Unitless, one;
    base {
        Meter, m, m;
        Second, s, s;
    }
}

Then you've created the MS type with units Meter and Second. But these are really aliases, where Meter is MS<P1, Z0> and Second is MS<Z0, P1>. Then, Unitless is MS<Z0, Z0> where P1 is the type for the number 1 and ZO is the type for the number 0.

There are some tutorials for using dimensioned here: http://paholg.com/project/dimensioned/

from dimensioned.

@droundy What do you mean by 'Radians should be dimensionless'? Is what I am saying not possible?

from dimensioned.

I just mean that radians have no units. It's the name for a dimensionless
quantity. In this sense degrees are analogous to dozens or miles, it's a
kind of a unit for things that are pure numbers, which don't actually have
dimension. This sort of "unit" is tricky, because it is kind of like
units, but doesn't work with the same kind of checking that we can use for
real dimensions.

Of course, if you don't want to actually do math, you can define angle as a
dimension without trouble, and then radians and degrees will both be
dimensions. The problem arises, for instance, when you want to find an
angle from the ratio of an arc length and a radius, or to write use the
first few terms in the Taylor expansion of a trig function. Or if you want
to integrate over the surface of a sphere.

On Wed, Dec 2, 2015, 6:30 PM Brendan Zabarauskas [email protected]
wrote:

@droundy https://github.com/droundy What do you mean by 'Radians should
be dimensionless'? Is what I am saying not possible?

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#5 (comment).

from dimensioned.

Hmm. It is really nice for documentation though, and picks up errors nicely if you mess up. Do you think dimensioned is overkill for this then?

from dimensioned.

I would find dimensioned to be overkill if all you want is to document that
you are taking degrees as input.

On Wed, Dec 2, 2015 at 7:01 PM Brendan Zabarauskas [email protected]
wrote:

Hmm. It is really nice for documentation though, and picks up errors
nicely if you mess up. Do you think dimensioned is overkill for this then?

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#5 (comment).

from dimensioned.

I am going to consider this closed. Feel free to re-open it if you have further questions, @bjz.

from dimensioned.

👍

from dimensioned.