The following code example is taken from the book
The C++ Standard Library - A Tutorial and Reference, 2nd Edition
by Nicolai M. Josuttis, Addison Wesley Longman, 2012
Copyright © 2012 by Pearson Education, Inc. and Nicolai M. Josuttis
#include <unordered_map>
#include <string>
#include <iostream>
using namespace std;
int main()
{
// type of the container:
// - unordered_map: elements are key/value pairs
// - string: keys have type string
// - float: values have type float
unordered_map<string,float> coll;
// insert some elements into the collection
// - using the syntax of an associative array
coll["VAT1"] = 0.16;
coll["VAT2"] = 0.07;
coll["Pi"] = 3.1415;
coll["an arbitrary number"] = 4983.223;
coll["Null"] = 0;
// change value
coll["VAT1"] += 0.03;
// print difference of VAT values
cout << "VAT difference: " << coll["VAT1"] - coll["VAT2"] << endl;
}