On Thursday, 13 May 2021 at 03:03:37 UTC, Tim wrote:
Hello all,
I have this piece of code
```D
/**
Rotate a 2D array (Vector) by phi radians
Params:
vec = 2D Vector to rotate
phi = Degree with which to rotate the Vector in radians
Returns:
Rotated 2D array (Vector)
Example:
*/
pragma(inline, true)
Point2 rotate2D(in Point2 vec, in float phi) pure nothrow {
double x = (vec[0]*cos(phi)) - (vec[1]*sin(phi));
double y = (vec[0]*sin(phi)) + (vec[1]*cos(phi));
return [x, y];
}
unittest{
auto p = rotate2D([0.0, 10.0], PI_2);
assert(p == [-10.0, 0.0]);
}
```
When I run the unittest, I get ```[-10, -4.37114e-07]``` back,
which is obviously wrong. Any idea as to why it's not making
the y-axis zero? Is it a rounding issue with the types I'm
using?
Thanks in advance
You should try to use isClose to compare for floats equality :
https://dlang.org/phobos/std_math.html#.isClose
Float arithmetic isn't exact, and could give unexpected results
like 0.1f + 0.2f != 0.3f
