set::const_reference
const 提供对元素的引用类型。的读取和执行 const 操作中集存储区。
typedef typename allocator_type::const_reference const_reference;
示例
// set_const_ref.cpp
// compile with: /EHsc
#include <set>
#include <iostream>
int main( )
{
using namespace std;
set <int> s1;
s1.insert( 10 );
s1.insert( 20 );
// Declare and initialize a const_reference &Ref1
// to the 1st element
const int &Ref1 = *s1.begin( );
cout << "The first element in the set is "
<< Ref1 << "." << endl;
// The following line would cause an error because the
// const_reference cannot be used to modify the set
// Ref1 = Ref1 + 5;
}
要求
标头: <set>
命名空间: std