c++ regex的一个错误？

下面的代码怎么了？为何for换内部不执行？

#include <string>
#include <iostream>
#include <regex>
#include <fstream>
using namespace std;
bool valid(const smatch &);
int main()
{
cout << "good" << endl;
string pattern("(\\()?(\\d{3})(\\))?([-.]?|[[:blank:]]*)(\\d{3})([[:blank:]]* | [.-]?)(\\d{4})");
regex r(pattern);
smatch results;
string line;
ifstream in("data.txt");
while(getline(in,line))
	{ 
	cout << "line:" << line << endl;
	for(sregex_iterator it(line.begin(),line.end(),r),end;it != end; ++ it)
		{
		cout << "for"<< endl;
		if(valid(*it))
			{ 
				cout << it -> str() << endl;
			}
		else
			{cout << it->str() << " is not legal." << endl;}
		}		
	
	}
	

	return 0;
}


bool valid(const smatch &s)
{
	if(s[1].matched)
		{
			return s[3].matched && (!s[4].matched || s[4].str() == " ");
		}


	else
		{
			return s[3].matched == 0 && (s[4].str() == s[6].str());
		}
}