do --- for-dir
  local a,b,c = 10,1,-1
  for i=1,20 do
    if c == -1 then
      a,b,c = 1,10,1
    else
      a,b,c = 10,1,-1
    end
    local x = 0
    for i=a,b,c do for j=1,10 do end x=x+1 end
    assert(x == 10)
  end
end