CSS line-height不影响float：right元素

I have two span elements that I'm trying to vertically center and I've managed to center the left element by matching the line-height with the height of the parent element however the right element which has a style of float:right is not affected by the line-height change, is there any reason for this and how can I vertically center the floated element too?I have two span elements that I'm trying to ver