math package - conversion functions between rad and grad

[Johann Höchtl]

The trigonometric functions of the math package operate on rads, the
mathematically sane way.

Most people operate in degrees. Conversion between these two systems
is trivial, but wouldn't it be a good fit if the math package contains

RadtoGrad(rad float64) float64

and

GradtoRad(grad float64) float64

-- Johann

[Rob 'Commander' Pike]

Surely you mean RadToDeg? No one I know has ever used a grad to measure an angle (puns aside).

-rob

[Michael Jones]

The construction industries use grads (gradients) which are 400 to a
circle, so a "3 percent slope" can be 3 grads, this is why the
angle-mode annunciator and button on HP calculators has 'DRG'

--
Michael T. Jones, Chief Technology Advocate, Google Inc.
1600 Amphitheatre Parkway, Mountain View, California 94043
Email: m...@google.com Mobile: 408-507-8160 Fax: 650-649-1938
Advancing the technology to organize the world's information and
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[Mehmet D. Akın]

Survey engineers, cartographers uses grad as well.

[Johann Höchtl]

Yes of course; A mistake trigered by the peculiarities of the german
language ;)

1 degree = 1/360 of a circle
1 grad = 1/400 of circle

But as noted, 'grads' may also have a point.

> -rob

[Michael Jones]

Do you propose functions, or are handy multiplicative constants good enough?

const (

DegToRad = 0.017453292519943295769236907684886127134428718885417 // N[Pi/180, 50]

RadToDeg = 57.295779513082320876798154814105170332405472466564   // N[180/Pi, 50]

GradToRad = 0.015707963267948966192313216916397514420985846996876 // N[Pi/200, 50]

RadToGrad = 63.661977236758134307553505349005744813783858296183   // N[200/Pi, 50]

)

--

Michael T. Jones

   Chief Technology Advocate, Google Inc.

   1600 Amphitheatre Parkway, Mountain View, California 94043

   Email: m...@google.com  Mobile: 650-335-5765  Fax: 650-649-1938

   Organizing the world's information to make it universally accessible and useful

[Rob 'Commander' Pike]

If necessary, I would advocate constants, easily and accurately
computed at compile time, as in:

const (
RadToDeg = 180/Pi
DegToRad = Pi/180
RadToGrad = 200/Pi
GradToDeg = Pi/200
)

-rob

[Johann Höchtl]

The overhead of a function call (in the absence of compile time
optimisation) make a constant solution certainly more appealing.

> -rob