Angles Done With Integers
Docs: https://docs.rs/integer_angles/
```rust
use integer_angles::Angle;
asserteq!(Angle::pi2().cos::(), 0.0f64);
```
Here we go, down the rabbit hole of floating-point instability and all sorts of crazy problems
that come with representing angles within computers. The goal of this library is to solve the
following problems:
- If you have multiple angles, and you add them together, the result you get should be exactly
correct.
- If you add multiple angles together and end up with a full circle, that should be exactly a
full circle.
- If you do trigonometry of some multiple of
pi
radians, you should end up with the exact
answer.
- Keep track of the difference between a
0
radian angle, and a 2 pi
radians angle.
- Keep track of if the angle is going clockwise or counter-clockwise starting at the positive x
axis.
- Do not allow the user to represent an angle outside the range [
-2 pi
to 2 pi
]
The way this library does it's magic is the following:
- Stores the angle in units of
[0..2**64)
where each unit is 1/(2**64)
th of a circle.
- This means that adding and subtracting angles (with wrapping) will always be correct, and
always within the specified range. (No more range reduction!)
- This also means that you can (inside the library) cast an angle from
u64
to i64
and
end up with the same angle.
- Set a flag for a full circle, and allow units to be
0
for a 0
degree angle.
- This also means, for example,
pi
radians is exactly equal to 1<<63
units in this library.
- Keep track of the clockwise/counterclockwise-ness of the angle using a separate flag.
- Solves the Chebyshev to compute the sin/cos/tan using the new units (with more precision
than the standard library).
- Uses a binary search (at the moment) to compute asin/acos/atan/atan2.
Caveats:
* This library is slower than using an f64 (about 10 times slower to compute cos
. You've
gotta wait a whole 80 ns to get the result!).
* ... Probably other things.
License: MIT