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What are some good tutorials on fold left? Original question, restored from deletion to provide context for other answers: I am trying to implement a method for finding the boudning box of rectangle, circle, location and the group which all extends Shape. Group is basically an array of Shapes abstract class Shape case class Rectangle(width: Int, height: Int) extends Shape case class Location(x: Int, y: Int, shape: Shape) extends Shape case class Circle(radius: Int) extends Shape case class Group(shape: Shape*) extends Shape I got the bounding box computed for all three except the Group one. So now for the bounding box method I know I should be using map and fold left for Group, but I just can't find out the exact syntax of creating it. object BoundingBox { def boundingBox(s: Shape): Location = s match { case Circle(c)=> new Location(-c,-c,s) case Rectangle(_, _) => new Location(0, 0, s) case Location(x, y, shape) => { val b = boundingBox(shape) Location(x + b.x, y + b.y, b.shape) } case Group(shapes @ _*) => ( /: shapes) { } // i dont know how to proceed here. } } Group bounding box is basically the smallest bounding box with all the shapes enclosed.

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