Scala: Draw table to console

Question

I need to display a table in a console.

My simple solution, if you would call it a "solution", is as follows:

  override def toString() = {
    var res = "\n"
      var counter = 1;
      res += stateDb._1 + "\n"
      res += "  +----------------------------+\n"
      res += "  +     State Table            +\n"
      res += "  +----------------------------+\n"
      for (entry <- stateDb._2) {
        res += "  | " + counter + "\t | " + entry._1 + " | " + entry._2 + " |\n"
        counter += 1;
      }
      res += "  +----------------------------+\n"
      res += "\n"
    res

  }

We don't have to argue this

• a is looking bad when displayed
• b code looks kinda messed up

Actually, such a question was asked for C# but I would like to know a nice solution for Scala as well.

So what is a (nice/good/simple/whatever) way to draw such a table in Scala to the console?

-------------------------------------------------------------------------
|    Column 1     |    Column 2     |    Column 3     |    Column 4     |
-------------------------------------------------------------------------
|                 |                 |                 |                 |
|                 |                 |                 |                 |
|                 |                 |                 |                 |
-------------------------------------------------------------------------

Answer 1

I've pulled the following from my current project:

object Tabulator {
  def format(table: Seq[Seq[Any]]) = table match {
    case Seq() => ""
    case _ => 
      val sizes = for (row <- table) yield (for (cell <- row) yield if (cell == null) 0 else cell.toString.length)
      val colSizes = for (col <- sizes.transpose) yield col.max
      val rows = for (row <- table) yield formatRow(row, colSizes)
      formatRows(rowSeparator(colSizes), rows)
  }

  def formatRows(rowSeparator: String, rows: Seq[String]): String = (
    rowSeparator :: 
    rows.head :: 
    rowSeparator :: 
    rows.tail.toList ::: 
    rowSeparator :: 
    List()).mkString("\n")

  def formatRow(row: Seq[Any], colSizes: Seq[Int]) = {
    val cells = (for ((item, size) <- row.zip(colSizes)) yield if (size == 0) "" else ("%" + size + "s").format(item))
    cells.mkString("|", "|", "|")
  }

  def rowSeparator(colSizes: Seq[Int]) = colSizes map { "-" * _ } mkString("+", "+", "+")
}

scala> Tabulator.format(List(List("head1", "head2", "head3"), List("one", "two", "three"), List("four", "five", "six")))
res1: java.lang.String = 
+-----+-----+-----+
|head1|head2|head3|
+-----+-----+-----+
|  one|  two|three|
| four| five|  six|
+-----+-----+-----+