A probe sequence policy using square increments.
| Parameter | Description | Default Value | 
| Const_Key_Ref | Const key reference type. | - | 
| Size_Type | Size type. | size_t | 
| Type | Definition | Description | 
| size_type | Size_Type | Size type. | 
| Method | Description | 
| void swap (quadratic_probe_fn &r_other) | Swaps content. | 
| Method | Description | 
| inline size_type operator() (Const_Key_Ref r_key, size_type i) const | Returns the i-th offset from the hash value. |