Type classes for a generic interpolate method

gistfile1.scala

// See: http://www.scala-notes.org/2010/08/a-generic-interpolate-method-using-type-classes/

// Trait for types that can be multiplied with a T, resulting in an R
trait Multipliable[-T, +R] {
  def *(value: T): R
}

// Trait for types to which a T can be added, resulting in an R
trait Addable[-T, +R] {
  def +(value: T): R
}

trait MultipliableSame[T] extends Multipliable[T, T]

trait AddableSame[T] extends Addable[T, T]

trait Interpolatable[T] extends Multipliable[Double, T] with AddableSame[T]

// Linearly interpolate between two values
 def interpolate[@specialized(Double) T <% Interpolatable[T]](t: Double, a: T, b: T): T = a * (1.0 - t) + b * t

// Make Double interpolatable
implicit def doubleToInterpolatable(n: Double) = new Interpolatable[Double] {
   def *(value: Double): Double = n * value
   def +(value: Double): Double = n + value
}