A Frame that models the domain more closely.

Frame.groovy

package bowling

class Frame 
{
  public add(roll) { rolls << roll }
  public addBonus(roll) { bonusRolls << roll }

  public score()
  {
    if(isStrike() || isSpare())
    {
      rolls.sum() + bonusRolls.sum()
    }
    else
    {
      rolls.sum()
    }
  }
  
  private rolls = []
  private bonusRolls = []
  
  public isStrike(){ roll(1) == 10 }
  public isSpare(){ (roll(1) + roll(2)) == 10 }
  
  private roll(n){ rolls[n-1] }
}