// In computer science, an associative array, map, symbol table, or dictionary is an abstract data type composed of a collection of (key, value) pairs, such that each possible key appears just once in the collection.
//
// Operations associated with this data type allow:
// - the addition of a pair to the collection
// - the removal of a pair from the collection
// - the modification of an existing pair
// - the lookup of a value associated with a particular key