C++11 新特性之 tuple

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我们在C++中都用过pair.pair是一种模板类型，其中包含两个数据值，两个数据的类型可以不同.pair可以使用make_pair构造

pair<int, string> p = make_pair(1, "a1");

如果传入的参数为多个，那么就需要嵌套pair，如下代码

#include <iostream>#include <map>using namespace std;int main(){//<int, string, string, string> ,注意：在嵌套模板实参列表中应当使用‘> >’而非‘>>’map<int, map<string, map<string, string> > > m; map<string, string> temp1;temp1.insert(make_pair("b1", "c1"));map<string, map<string, string> > temp2;temp2.insert(make_pair("a1", temp1));m.insert(make_pair(1, temp2));map<string, string> temp3;temp3.insert(make_pair("b2", "c2"));map<string, map<string, string> > temp4;temp4.insert(make_pair("a2", temp3));m.insert(make_pair(2, temp4));//遍历map<int, map<string, map<string, string> > >::const_iterator itr1;map<string, map<string, string> >::const_iterator itr2;map<string, string>::const_iterator itr3;for (itr1=m.begin(); itr1!=m.end(); itr1++){cout << itr1->first << " ";itr2 = (itr1->second).begin();    cout << itr2->first << " ";    itr3 = (itr2->second).begin();    cout << itr3->first << " ";    cout << itr3->second << endl;}pair<int, string> p = make_pair(1, "a1");return 0;}

上面的做法明显很麻烦，在C++11中引入了变长参数模板,所以发明了新的数据类型:tuple,tuple是一个N元组,可以传入1个, 2个甚至多个不同类型的数据，避免了嵌套pair的丑陋做法，通过make_tuple()创建元组，通过get<>()来访问元组的元素

#include <iostream>#include <tuple>#include <vector>using namespace std;int main(){auto t1 = make_tuple(1, "a1", "b1", "c1");cout << get<0>(t1) << " ";cout << get<1>(t1) << " ";cout << get<2>(t1) << " ";cout << get<3>(t1) << " ";cout << endl;vector<tuple<int, string, string, string> > tv;tv.push_back(make_tuple(1, "a1", "b1", "c1"));tv.push_back(make_tuple(2, "a2", "b2", "c2"));vector<tuple<int, string, string, string> >::iterator itr;for (itr=tv.begin(); itr!=tv.end(); itr++){cout << get<0>(*itr) << " ";cout << get<1>(*itr) << " ";cout << get<2>(*itr) << " ";cout << get<3>(*itr) << endl;}return 0;}

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