less-条件表达式

//.mixin (@a) when (lightness(@a) >= 50%) {   //255/2=127.5
//  background-color: black;
//}
//.mixin (@a) when (lightness(@a) < 50%) {
//  background-color: white;
//}
//.mixin (@a) {
//  color: @a;
//}
//.class1 { .mixin(#7e7e7e) }  //221  > 127.5  >50%  background-color: black;  7e7e7e  =  126
//.class2 { .mixin(#808080) }  //85 <127.5  <50%   background-color: white;  808080 = 128

//iscolor,isnumber.....判断值得类型
//.mixin (@a) when (iscolor(@a)) {   //255/2=127.5
//  background-color: black;
//}
//.mixin (@a) when (isnumber(@a) ) {
//  background-color: white;
//  shuzi:shuzi;
//}
//.mixin (@a) {
//  color: @a;
//}
//.class1 { .mixin(#7e7e7e) }  //background-color: black;
//.class2 { .mixin(123) }  //background-color: white;


//ispixel,ispercentage.....单位检查函数
.mixin (@a) when (ispixel(@a)) {
  background-color: black;
}
.mixin (@a) when (ispercentage(@a) ) {
  background-color: white;
}
.mixin (@a) {
  width: @a;
}
.class1 { .mixin(960px) }  //background-color: black; width:960px
.class2 { .mixin(95%) }  //background-color: white;width:95%