a semantic grid mixin for Stylus, better with PR <https://github.com/LearnBoost/stylus/pull/1048>

grid.styl

grid-ctn(containerwidth, col, padwidth = grid-devide(containerwidth, col * 8))
  $grid_width grid-devide(containerwidth, col)
  $grid_col col
  $grid_padding grid-devide(padwidth, 2)

  width containerwidth
  position relative
  clearfix()

grid-block(colspan)
  require-unit(@$grid_width)
  require-unit(@$grid_padding)

  float left
  width (colspan * @$grid_width) - 2 * unit(@$grid_padding, '')
  margin-left @$grid_padding
  margin-right @$grid_padding

grid-full-block()
  grid-block(@$grid_col)

grid-pull(colspan)
  require-unit(@$grid_width)
  margin-right colspan * @$grid_width + unit(@margin-right, '')

grid-push(colspan)
  require-unit(@$grid_width)
  margin-left colspan * @$grid_width + unit(@margin-left, '')

grid-devide(width, division)
  u = unit(width)
  num = unit(width, '')

  unit(floor(num / division * 1000) / 1000, u)