By Andrew J. Wozniewicz
Milwaukee, August 5, 2008

Here is an example showing how to use loops in WANTScript.

There are three kinds of loop constructs available right now: WHILE-loop, REPEAT-loop, and FOR-loop. One difference with Pascal is that the FOR-loop has an optional step clause (alas, not illustrated in the example below).

Also, the keyword loop can be used instead of do, and/or repeat, so that while-do is equivalent to while-loop, for-do is equivalent to for-loop, and repeat-until is equivalent to loop-until. In other words, loop can appear whenever do can appear, and vice versa; likewise, loop can appear whenever repeat can appear, and vice-versa.

project FloydsTriangle //Test190

{
Loops. WHILE-DO, FOR-TO, REPEAT-UNTIL
}

  WriteLn("Floyd's Triangle using WHILE loop")
  FloydsTriangleWHILE(5)
  WriteLn
  WriteLn("Floyd's Triangle using FOR loop")
  FloydsTriangleFOR(5)
  WriteLn
  WriteLn("Floyd's Triangle using REPEAT loop")
  FloydsTriangleUNTIL(5)

  {
    Floyd's triangle is a right angled triangular array of natural numbers.
    It is named after Robert Floyd. It is defined by filling the rows of
    The triangle with consecutive numbers, starting with a 1 in the top
    left corner:

    1
    2 3
    4 5 6
    7 8 9 10
    11 12 13 14 15

    The numbers along the right edge of the triangle are the
    triangular numbers.

    Source: www.wikipedia.org/wiki/Floyd%27s_triangle
  }

  import System.Utilities

  procedure FloydsTriangleFOR(MaxRows)
    var Row, Column
    var Number

    Number = 0
    for Row := 1 to MaxRows loop
      for Column := 1 to Row do
        Number++
        Write( PadLeft(Number,3) )
      end
      WriteLn
    end
  end


  procedure FloydsTriangleWHILE(MaxRows)
    var Row, Column
    var Number

    Number = 0
    Row := 1
    while Row <= MaxRows loop
      Column := 1
      while Column <= Row do
        Number++
        Write( PadLeft(Number,3) )
        Column++
      end
      WriteLn
      Row++
    end
  end


  procedure FloydsTriangleUNTIL(MaxRows)
    var Row, Column
    var Number

    Number = 0
    Row := 1
    loop
      Column := 1
      while Column <= Row do
        Number++
        Write( PadLeft(Number,3) )
        Column++
      end
      WriteLn
      Row++
    until Row > MaxRows
  end

end

Floyd's Triangle using WHILE loop
  1
  2  3
  4  5  6
  7  8  9 10
 11 12 13 14 15

Floyd's Triangle using FOR loop
  1
  2  3
  4  5  6
  7  8  9 10
 11 12 13 14 15

Floyd's Triangle using REPEAT loop
  1
  2  3
  4  5  6
  7  8  9 10
 11 12 13 14 15

-Andrew