去掉字符串左右两端空白字符串

#include <functional>
#include <algorithm>

using namespace std;

string& lTrim(string &ss)
{
string::iterator p=find_if(ss.begin(),ss.end(),not1(ptr_fun(isspace)));
ss.erase(ss.begin(),p);
return ss;
}
string& rTrim(string &ss)
{
string::reverse_iterator  p=find_if(ss.rbegin(),ss.rend(),not1(ptr_fun(isspace)));
ss.erase(p.base(),ss.end());
return ss;
}
string& trim(string &st)
{
lTrim(rTrim(st));
return st;
}