Pascal's triangle in scala

pascal.scala

def pascal(c: Int, r: Int): Int = {
    if (c < 0 || r < 0 || c > r) throw new IllegalArgumentException("Column and row numbers must be 0 or greater. Column length must be lower than row length") else{
      if (c == 0 || c == r) 1 else {
        pascal(c - 1, r - 1) + pascal(c, r - 1)
      }
    }
  }