:idprefix: hash_equality_

```cpp template < class Key, class Mapped, class Hash = boost::hash<Key>, class Pred = std::equal_to<Key>, class Alloc = std::allocator<std::pair<Key const, Mapped> > > class unordered_map; ```

There is an link:../../../examples/fnv1.hpp[implementation of FNV-1a^] in the examples directory.

If you wish to use a different equality function, you will also need to use a matching hash function. For example, to implement a case insensitive dictionary you need to define a case insensitive equality predicate and hash function:

for(std::string::const_iterator it = x.begin(); it != x.end(); ++it) { boost::hash_combine(seed, std::toupper(*it, locale)); }

return seed; } }; ```

```cpp struct point { int x; int y; };

bool operator==(point const& p1, point const& p2) { return p1.x == p2.x && p1.y == p2.y; }

```cpp struct point { int x; int y; };

bool operator==(point const& p1, point const& p2) { return p1.x == p2.x && p1.y == p2.y; }

`hasher hash_function() const`

`key_equal key_eq() const`