src/styles/mixins/layout.less

@row-prefix-cls: ~"@{css-prefix}row";
@col-prefix-cls: ~"@{css-prefix}col";
.make-row(@gutter: @grid-gutter-width) {
    position: relative;
    margin-left: (@gutter / -2);
    margin-right: (@gutter / -2);
    height: auto;
    .clearfix;
}
.float-grid-columns(@class) {
    .col(@index) { // initial
        @item: ~".@{col-prefix-cls}-span@{class}-@{index}";
        .col((@index + 1), @item);
    }
    .col(@index, @list) when (@index =< @grid-columns) { // general
        @item: ~".@{col-prefix-cls}-span@{class}-@{index}";
        .col((@index + 1), ~"@{list}, @{item}");
    }
    .col(@index, @list) when (@index > @grid-columns) { // terminal
        @{list} {
            float: left;
            flex: 0 0 auto;
        }
    }
    .col(1); // kickstart it
}
.loop-grid-columns(@index, @class) when (@index > 0) {
    .@{col-prefix-cls}-span@{class}-@{index} {
        display: block;
        width: percentage((@index / @grid-columns));
    }
    .@{col-prefix-cls}@{class}-push-@{index} {
        left: percentage((@index / @grid-columns));
    }
    .@{col-prefix-cls}@{class}-pull-@{index} {
        right: percentage((@index / @grid-columns));
    }
    .@{col-prefix-cls}@{class}-offset-@{index} {
        margin-left: percentage((@index / @grid-columns));
    }
    .@{col-prefix-cls}@{class}-order-@{index} {
        order: @index;
    }
    .loop-grid-columns((@index - 1), @class);
}
.loop-grid-columns(@index, @class) when (@index = 0) {
    .@{col-prefix-cls}-span@{class}-@{index} {
        display: none;
    }
    .@{col-prefix-cls}@{class}-push-@{index} {
        left: auto;
    }
    .@{col-prefix-cls}@{class}-pull-@{index} {
        right: auto;
    }
    .@{col-prefix-cls}@{class}-offset-@{index} {
        margin-left: 0;
    }
    .@{col-prefix-cls}@{class}-order-@{index} {
        order: 0;
    }
}
.make-grid(@class: ~'') {
    .float-grid-columns(@class);
    .loop-grid-columns(@grid-columns, @class);
}