less的预处理

.flex(@a:1){-webkit-flex:@a;-ms-flex:@a;flex:@a;}
.fl{float:left;}
.fr{float:right;}
.df{display:-webkit-flex;display:-ms-flexbox;display:flex;}
.poa(@left:0px,@top:0px){position:absolute;left:@left;top:@top;}
.pof(@left:0px,@top:0px){position:fixed;left:@left;top:@top;}
.pos(@left:0px,@top:0px){position:relative;left:@left;top:@top;}
.w(@0,@height:0){@width;height:@height;}
.m(@l:0,@t:0,@r:0,@b:0){margin:@t,@r,@b,@l;}
.p(@l:0,@t:0,@r:0,@b:0){padding:@t,@r,@b,@l;}
.lh(@lh){line-height:@lh;}
.fz(@fz:0){font-size:@fz;}
.bg(@bg:0){background:@bg;}
.c(@color){color:@color;}
.tac{text-align:center;}
.bd(@color){border:1px solid @color;}
.transition(@time:1s,@prop:all,@ease:ease-in-out){-webkit-transition:@prop @time @ease;-moz-transition:@prop @time @ease;-o-transition:@prop @time @ease;transition:@prop @time @ease;}
.op(@opacity){@opa:(@opacity*100);filter:alpha(opacity=@opa);opacity:@opacity;}
.text-hide{display:block;font-size:0;text-indent:-99999em;color:transparent;}
.omit{white-space:nowrap;overflow:hidden;text-overflow:ellipsis;}