Q：假設我們現在需要一個string*的set，我們向其插入一些動物到這個set中：
<*> ssp; ssp.insert( ( ( ( ());
You then write the following code to print the contents of the set, expecting the strings to come out in alphabetical order. After all, sets keep their contents sorted.
<< i << endl;
真正打印出來的會是字符串的指針值。或許你說那我在i前面加個*，取出字符串不就搞定了，so easy！是可以，但是別忘了我們的需求，我們需要使得字符串有序排列，而這樣得到的只是對指針值有序排列了，顯然不滿足我們得要求！
其實我們上述的語句set<string*> ssp;是下面語句的簡化寫法：
set<string*, less<string*> > ssp;
If you want the string* pointers to be stored in the set in an order determined by the string values, you can’t use the default comparison functor class less<string*>. You must instead write your own comparison functor class, one whose objects take string* pointers and order them by the values of the strings they point to. Like this:
binary_function< *, *, > ()( *ps1, *ps2) *ps1 < *
Then you can use StringPtrLess as ssp’s comparison type:
typedef <*, StringPtrLess>
好了，最終的解決方案出爐了：
typedef <*, StringPtrLess> ( ( ( (<< *i <<
當然，其中的打印過程可以有很多花樣，比如我也可以利用alogrithm來完成，也是OK的。
If you want to use an algorithm instead, you could write a function that knows how to dereference string* pointers before printing them, then use that function in conjunction with for_each:
print( *<< *ps <<
感謝大家的閱讀，希望能幫到大家！
Published by Windows Live Writer.
