Each instance of this class represents a direction on a two-dimensional plane. A direction consists of two components: dx and dy, each of which is a number between -1.0 and +1.0 (inclusive). dx indicates the degree to which the x coordinate changes when moving in that direction; dy is the same for the y coordinate. The x coordinate increases rightwards and y downwards.
For example, moving straight rightwards can be thought of a moving in a Direction with a dx of +1.0 and a dy of 0.0; by comparison, the upward direction would have a dx of 0.0 and a dy of -1.0. . Diagonals have non-zero values for both dx and dy.
The dx and dy of any Direction always sum up to (roughly) 1.0, with the exception of the special value NoDirection which represents the lack of a direction and as zero for both components. (In this, a Direction is different than a Velocity, which is a combination of a direction of movement and a speed.)
You don’t instantiate Direction directly; instead, you create Directions with the methods on this class’s companion object. Among other things, you can:
- construct a direction from two differences between coordinates, as in
Direction.fromDeltas(-100, 50); or - create a direction that corresponds to a given angle, as in
Direction.fromDegrees(60)andDirection.fromRadians(-scala.math.Pi / 4).
Some of the methods of a Direction object also create and return new Directions, as does the directionOf method on Pos objects. Moreover, this class’s companion object has a few predefined Direction constants: Up Down, Left, Right, and NoDirection.
Direction objects are immutable.
This class has an alias in the top-level package o1, so it’s accessible to students simply via import o1.*.
Parameters
- dx
-
the amount of change in the x coordinate when moving in this direction, relative to
dy - dy
-
the amount of change in the y coordinate when moving in this direction, relative to
dx
Attributes
- Companion
- object
- Graph
-
- Supertypes