## UniqueHashFunction

### Definition

UniqueHashFunction is a concept for a hash function with unique hash values. An instance hash for a model of the UniqueHashFunction concept is a function object. It maps objects of its domain type Key to the integral image type std::size_t. The image values have to be unique for all keys in the domain type Key.

### Refines

STL concept HashFunction.

### Types

typedef std::size_t
| result_type; | type of the hash value.

### Creation

UniqueHashFunction hash ( hash2);
| copy constructor.

UniqueHashFunction&
| hash = hash2 | assignment.

### Operations

std::size_t | hash ( Key key) | returns unique hash value for the key value.

### Has Models

CGAL::Handle_hash_function

### See Also

CGAL::Unique_hash_map<Key,Data,UniqueHashFunction>