http://codepen.io/thybzi/pen/xOmmOj?editors=0100

position.less

/**
 * Apply position value, and 0 to 4 offset values
 * Offsets (length or `auto`) are treated similar to `padding` value
 * Any of offsets may be `null`, in that case it is counted but not used
 * @example .position(absolute, 5px, 2px)       // position: absolute, 5px for top and bottom, 2px for left and right
 * @example .position(relative, 5px, 2px, 3px)  // position: relative, top: 5px, bottom: 3px, 2px for left and right
 * @example .position(fixed, 5px, 2px, null)    // position: fixed, top: 5px, nothing for bottom, 2px for left and right
 * @example .position(static)                   // applies just `position: static` (without any offsets)
 */
.position(@value, @offsets...) when (iskeyword(@value)) {
    @count: length(@offsets);

    & {
        position: @value;
    }

    & when (@count >= 4) {
        .offset(left, extract(@offsets, 4));
        .offset(right, extract(@offsets, 2));
        .offset(top, extract(@offsets, 1));
        .offset(bottom, extract(@offsets, 3));
    }

    & when (@count = 3) {
        @left-right: extract(@offsets, 2);
        .offset(left, @left-right);
        .offset(right, @left-right);
        .offset(top, extract(@offsets, 1));
        .offset(bottom, extract(@offsets, 3));
    }

    & when (@count = 2) {
        @left-right: extract(@offsets, 2);
        @top-bottom: extract(@offsets, 1);
        .offset(left, @left-right);
        .offset(right, @left-right);
        .offset(top, @top-bottom);
        .offset(bottom, @top-bottom);
    }

    & when (@count = 1) {
        .offset(left, @offsets);
        .offset(right, @offsets);
        .offset(top, @offsets);
        .offset(bottom, @offsets);
    }

    .offset(@side, @value) when (isnumber(@value)), (@value = auto) {
        @{side}: @value;
    }
}

/**
 * Apply `position: absolute`, and 0 to 4 offset values
 * Offsets (length or `auto`) are treated similar to `padding` value
 * Any of offsets may be `null`, in that case it is counted but not used
 * @example .absolute(5px, 2px)       // applies 5px for top and bottom, 2px for left and right
 * @example .absolute(5px, 2px, 3px)  // applies 5px for top, 3px for bottom, 2px for left and right
 * @example .absolute(5px, 2px, null) // applies 5px for top, nothing for bottom, 2px for left and right
 * @example .absolute()               // applies just `position: absolute` (without any offsets)
 */
.absolute(@offsets...) {
    .position(absolute, @offsets);
}

/**
 * Apply `position: fixed`, and 0 to 4 offset values
 * Offsets (length or `auto`) are treated similar to `padding` value
 * Any of offsets may be `null`, in that case it is counted but not used
 * @example .fixed(5px, 2px)       // applies 5px for top and bottom, 2px for left and right
 * @example .fixed(5px, 2px, 3px)  // applies 5px for top, 3px for bottom, 2px for left and right
 * @example .fixed(5px, 2px, null) // applies 5px for top, nothing for bottom, 2px for left and right
 * @example .fixed()               // applies just `position: fixed` (without any offsets)
 */
.fixed(@offsets...) {
    .position(fixed, @offsets);
}

/**
 * Apply `position: relative`, and 0 to 4 offset values
 * Offsets (length or `auto`) are treated similar to `padding` value
 * Any of offsets may be `null`, in that case in is counted but not used
 * @example .relative(5px, 2px)       // applies 5px for top and bottom, 2px for left and right
 * @example .relative(5px, 2px, 3px)  // applies 5px for top, 3px for bottom, 2px for left and right
 * @example .relative(5px, 2px, null) // applies 5px for top, nothing for bottom, 2px for left and right
 * @example .relative()               // applies just `position: relative` (without any offsets)
 */
.relative(@offsets...) {
    .position(relative, @offsets);
}