Full-width container inside limited width parent

<div class="parent">
<div class="full-width"> ... </div>
</div>

.parent {
    max-width:800px;
    margin-left:auto;
    margin-right:auto;
}
.full-width {
    width: 100vw;
    position: relative;
    left: 50%;
    right: 50%;
    margin-left: -50vw;
    margin-right: -50vw;
	  clear:both;
}