less size mixin
//less mixin
.size(@string) {
@w: ~`(function(a){ return a.split(" x ").shift()+"px"; })( @{string})`;
@h: ~`(function(a){ return a.split(" x ").pop()+"px"; })( @{string})`;
width:@w;
height:@h;
}
//usage
#myId{
.size("225 x 305");
}
//result
#myId{
width:225px;
height:305px;
}