# PairHash

This structure is a functional object (providing operator()) that generates a hash value for pairs. It is particularly used for hashing pairs consisting of a type\_index and an int, which is a common pattern in entity-component systems for associating components with entities.

```cpp
struct PairHash {
    /**
     * @brief Generates a hash value for a std::pair<std::type_index, int>.
     * 
     * Combines the hash of the type_index and int from the pair to create a unique hash value.
     * 
     * @param pair The pair of std::type_index and int to be hashed.
     * @return std::size_t The resulting hash value.
     */
    std::size_t operator()(const std::pair<std::type_index, int>& pair) const {
        return std::hash<std::type_index>()(pair.first) ^ std::hash<int>()(pair.second);
    }
};
```


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