angles.scala

package angles

import spire.algebra._
import scala.math.Pi

object Angle {
  def apply(n: Double): Angle =
    if (n < 0.0) new Angle(n % 360.0 + 360.0) else new Angle(n % 360.0)
  def fromRadians(n: Double): Angle =
    Angle(n * 360.0 / (2.0 * Pi))
  def fromDegrees(n: Double): Angle =
    Angle(n)

  implicit def order: Order[Angle] =
    new Order[Angle] {
      override def eqv(x: Angle, y: Angle): Boolean = x.theta == y.theta
      def compare(x: Angle, y: Angle): Int = x compare y
    }

  implicit def additive: AdditiveGroup[Angle] =
    new AdditiveGroup[Angle] {
      def zero: Angle = new Angle(0.0)
      def plus(x: Angle, y: Angle): Angle = x + y
      def negate(x: Angle): Angle = -x
      override def minus(x: Angle, y: Angle): Angle = x - y
    }
}

class Angle(val theta: Double) extends AnyVal { lhs =>
  override def toString(): String =
    theta.toString
  def compare(rhs: Angle): Int =
    lhs.theta compare rhs.theta
  def unary_-(): Angle =
    if (theta == 0.0) this else new Angle(360.0 - theta)
  def +(rhs: Angle): Angle =
    Angle(lhs.theta + rhs.theta)
  def -(rhs: Angle): Angle =
    Angle(lhs.theta - rhs.theta)

  def *(rhs: Double): Angle =
    Angle(lhs.theta * rhs)
  def /(rhs: Double): Angle =
    Angle(lhs.theta / rhs)
  def %(rhs: Double): Angle =
    Angle(lhs.theta % rhs)

  def toDegrees: Double = lhs.theta
  def toRadians: Double = lhs.theta * 2.0 * Pi / 360.0
}