gistfile1.nim

const WIDTH = 640
const HEIGHT = 400

type
  TField = tuple [
    a: float,
    b: float,
    c: float,
    d: float,
    e: float]
  TRow = array[0..WIDTH - 1, TField]
  TGrid = array[0..HEIGHT -1, TRow]
  TWorld = tuple [grid: TGrid]
  PWorld = ref TWorld

iterator mitems[IDX, T](x: var array[IDX, T]): var T =
  for i in low(x)..high(x):
    yield x[i]

proc display(world: var TWorld) =
  for row in mitems(world.grid):
    for field in mitems(row):
      echo("field")

var w: TWorld

w.display()