functional 2048

f2048

//todo: use vector, scala 2:10 generic extractors. Currently using 2.9, so List has better pattern matching support
type Row = List[Option[Int]]


def shiftR(r: Row): Row = r.foldRight(Nil: Row){ 
  case (None, acc) => acc
  case (Some(x), Some(a)::as) if a == x => Some(a + x)::as
  case (Some(x), acc) => Some(x)::acc
}.padTo(4, None)

def shiftL(r: Row): Row = r.foldLeft(Nil: Row){ 
  case (acc, None) => acc
  case (Some(a)::as, Some(x)) if a == x => Some(a + x)::as
  case (acc, Some(x)) => Some(x)::acc
}.reverse.padTo(4, None)

/*
use transpose to get at columns (need to ensure all dimensions are same somehow)

scala> val x = List(List(1,2,3), List(4,5,6), List(7,8,9))
x: List[List[Int]] = List(List(1, 2, 3), List(4, 5, 6), List(7, 8, 9))

scala> x.transpose
res13: List[List[Int]] = List(List(1, 4, 7), List(2, 5, 8), List(3, 6, 9))

scala> x.transpose.transpose == x
res15: Boolean = true
*/

/*
use padTo(n, elem) to pad out lists to size n by appending elem
*/

//also, command line interface!

def print(b: Board) = b.map(_.map(_.map(_.toString).getOrElse(".")).mkString("")).mkString("\n")