10.22

#include <iostream>
#include <fstream>
#include <vector>
#include <string>
#include <algorithm>

using namespace std;
using namespace std::placeholders;

void output_words(const string &s)
{
	for(auto iter = s.begin(); iter != s.end() ; ++iter)
		cout << *iter << " ";
	cout << endl;
}

bool compared6(const string &s, vector<string>::size_type sz)
{
	return s.size() <= sz;
}

int main(int argc, char *argv[])
{
	ifstream in(argv[1]);
	if (!in)
	{
		cerr << "無法開啟檔案" << endl;
		exit(1);
	}
	vector<string> words;
	string word;
	while(in >> word)
		words.push_back(word)；
	output_words(words);

	auto bz = count_if(words.begin(), words.end(), bind(compared6, _1, 6));
	cout <<bc <<  endl;
	return 0;
}
 

答案

#include <iostream>
#include <fstream>
#include <vector>
#include <string>
#include <algorithm>
#include <functional>
#include "make_plural.h"

using namespace std;
using namespace std::placeholders;

inline void output_words(const vector<string> &s)
{
	for(auto iter = s.begin(); iter != s.end() ; ++iter)
		cout << *iter << " ";
	cout << endl;
}

bool compared6(const string &s, string::size_type sz)
{
	return s.size() <= sz;
}

void biggies(vector<string> &words, vector<string>::size_type sz)
{
	output_words(words);
	auto bc = count_if(words.begin(0, words.end(), bind(compared6, _1, sz));
	cout << bc << endl;
}
int main(int argc, char *argv[])
{
	ifstream in(argv[1]);
	if (!in)
	{
		cerr << "無法開啟檔案" << endl;
		exit(1);
	}
	vector<string> words;
	string word;
	while(in >> word)
		words.push_back(word)；
	
	biggies(words, 6);
	
	return 0;
}
 

10.23 答案 bind是可變引數。它接受的第一個引數是一個可呼叫物件，即實際工作函式A，返回供演算法使用的新的可呼叫函式B。若A接受x個引數，則bind的引數個數應該是x+1，即除了A外，其他引數應一一對應A所接受的引數。這些引數中有一部分來自於B（_n），另外來自於所處函式的區域性變數。

10.24