less 编写函数与循环调用

@default-space: {
  top: 12;
  bottom: 12;
  left:12;
  right:12;
};

.margin(@space,@index) when (@index>0){
  @value:~'@{index}px';
  .mg-@{space}-@{index}{
    margin-@{space}:@value;
  }
}
.padding(@space,@index) when (@index>0){
  @value:~'@{index}px';
  .pd-@{space}-@{index}{
    padding-@{space}:@value;
  }
}
each(@default-space, {
  .margin(@key,@value);
  .padding(@key,@value);
});