rotate90 method

Pos rotate90([ int steps = 1 ])

Returns this position rotated by 90 degrees steps times clockwise.

The default is to rotate 90 degrees once, but you can rotate multiple times by providing a different number of steps, or counter-clockwise by providing a negative number of steps.

A 90° rotation is a fixed-point rotation, i.e. it does not use floating point numbers or π, and is derived entirely from integer offsets.

See rotate45 for 45° rotations.

Visualizing the rotations

Imagine the following original position, perhaps at (3, 2):

y
^
|
|    *
|
O-----> x

A 90° Clockwise rotate90() would move the position to (2, -3):

O-----> x
|
|
|  *
v
y

A 180° Clockwise rotate90(2) would move the position to (-3, -2):

x <-----O
        |
   *    |
        |
        v
        y

And finally, a 270° Clockwise rotate90(-1) is (-2, 3):

        y
        ^
     *  |
        |
        |
x <-----O

Example

final a = Pos(10, 20);
print(a.rotate90()); // => Pos(20, -10)
print(a.rotate90(2)); // => Pos(-10, -20)
print(a.rotate90(-1)); // => Pos(-20, 10)

Implementation

Pos rotate90([int steps = 1]) {
  return switch (steps % 4) {
    0 => this,
    1 => Pos(-y, x),
    2 => Pos(-x, -y),
    _ => Pos(y, -x),
  };
}