end
function test_skip_past_tab_to_previous_word()
  io.write('\ntest_skip_past_tab_to_previous_word')
  App.screen.init{width=120, height=60}
  Lines = load_array{'abc def\tghi'}
  Cursor1 = {line=1, pos=10}  -- within third word
  Margin_right = 0; Margin_width = Margin_left
  App.draw()
  App.run_after_keychord('M-left')
  check_eq(Cursor1.pos, 9, 'F - test_skip_past_tab_to_previous_word')

function test_skip_past_tab_to_next_word()
  io.write('\ntest_skip_past_tab_to_next_word')
  App.screen.init{width=120, height=60}
  Lines = load_array{'abc\tdef'}
  Cursor1 = {line=1, pos=1}  -- at the space between words
  Margin_right = 0; Margin_width = Margin_left
  App.draw()
  App.run_after_keychord('M-right')
  check_eq(Cursor1.pos, 4, 'F - test_skip_past_tab_to_next_word')
end

    local offset = Text.offset(Lines[Cursor1.line].data, Cursor1.pos)
    assert(offset > 1)
    if Lines[Cursor1.line].data:sub(offset-1,offset-1) == ' ' then

    if Text.match(Lines[Cursor1.line].data, Cursor1.pos-1, '%s') then

    local offset = Text.offset(Lines[Cursor1.line].data, Cursor1.pos)
    if Lines[Cursor1.line].data:sub(offset,offset) == ' ' then  -- TODO: other space characters

    if Text.match(Lines[Cursor1.line].data, Cursor1.pos, '%s') then

end
function Text.match(s, pos, pat)
  local start_offset = Text.offset(s, pos)
  assert(start_offset)
  local end_offset = Text.offset(s, pos+1)
  assert(end_offset > start_offset)
  local curr = s:sub(start_offset, end_offset-1)
  return curr:match(pat)