unordered_map::at
Finds an element in a unordered_map with a specified key value.
Ty& at(const Key& _Key);
const Ty& at(const Key& _Key) const;
Parameters
Parameter |
Description |
_Key |
The key value to find. |
Return Value
A reference to the data value of the element found.
Remarks
If the argument key value is not found, then the function throws an object of class out_of_range.
Example
// unordered_map_at.cpp
// compile with: /EHsc
#include <unordered_map>
#include <iostream>
typedef std::unordered_map<char, int> Mymap;
int main()
{
Mymap c1;
c1.insert(Mymap::value_type('a', 1));
c1.insert(Mymap::value_type('b', 2));
c1.insert(Mymap::value_type('c', 3));
// find and show elements
std::cout << "c1.at('a') == " << c1.at('a') << std::endl;
std::cout << "c1.at('b') == " << c1.at('b') << std::endl;
std::cout << "c1.at('c') == " << c1.at('c') << std::endl;
return (0);
}
Output
c1.at('a') == 10
c1.at('b') == 20
c1.at('c') == 30
Requirements
Header: <unordered_map>
Namespace: std