// 两行自适应
// @offset 参数表示上下内边距+边框的值
// 上栏定高，下栏自适应
.row2(@height, @offset: 0, @top: '>:first-child', @bottom: '>:nth-child(2)') {
    @top_selector: e(@top);
    @bottom_selector: e(@bottom);

    @{top_selector} {
        .position(0 0 auto 0);
        .set-height(@height);
    }
    @{bottom_selector} {
        .fit(@height + @offset 0 0 0);
    }
}

// 下栏定高，上栏自适应
.row2-b(@height, @offset: 0, @top: '>:first-child', @bottom: '>:nth-child(2)') {
    @top_selector: e(@top);
    @bottom_selector: e(@bottom);

    @{top_selector} {
        .fit(0 0 @height + @offset 0);
    }
    @{bottom_selector} {
        .position(auto 0 0 0);
        .set-height(@height);
    }
}

// 三行自适应
.row3(@top_height,
    @bottom_height,
    @top_offset: 0,
    @bottom_offset: 0,
    @top: '>:first-child',
    @middle: '>:nth-child(2)',
    @bottom: '>:nth-child(3)') {

    @top_selector: e(@top);
    @middle_selector: e(@middle);
    @bottom_selector: e(@bottom);

    @{top_selector} {
        .position(0 0 auto 0);
        .set-height(@top_height);
    }
    @{middle_selector} {
        .fit(@top_height + @top_offset 0 @bottom_height + @bottom_offset 0);
    }
    @{bottom_selector} {
        .position(auto 0 0 0);
        .set-height(@bottom_height);
    }
}