.col-generate(@n, @i: 1) when(@i <=@n) {
  .@{prefix}-col--@{i} {
    width: (@i * 100% / @n);
  }

  .@{prefix}-col--offset-@{i} {
    margin-left: (@i * 100% / @n);
  }

  .col-generate(@n, (@i + 1));
}