//.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%

.class1 {

  background-color: black;

  width: 960px;

}

.class2 {

  background-color: white;

  width: 95%;

}