so far as,so long as,as far as,so far as的区别?

so long as 1 只要 既然
He need not step down so long as they support him.
只要他们支持他,他就不必辞职．
2 由于
as far as＝so far as 1 到...那么远
例:The children walked as far as the lake.孩子们一直走到湖边
2 （表示程度 范围）就．．．；尽．．．；至于
例：as far as I know 就我所知
as far as possible 尽可能
（我已尽力了 希望对你有用）