This class provides a wrapper around a functor satisfying the Hash requirements ({`bslstl_hash`}) such that the function call operator is always declared as const qualified.

Synopsis

Declared in <bslstl_hashtable.h>

template<class FUNCTOR>
class HashTable_HashWrapper;

Description

TBD Provide an optimization for the case of an empty base functor, where we can safely const_cast want calling the base class operator.

Note that we would only one class, not two, with C++11 variadic templates and perfect forwarding, and we could also easily detect whether or not FUNCTOR provided a const‐qualified operator().

Member Functions

Name

Description

HashTable_HashWrapper [constructor]

Constructors

functor

Return a reference providing non‐modifiable access to the hash functor wrapped by this object.

operator()

Call the wrapped functor with the specified arg and return the result. Note that ARG_TYPE will typically be deduced as a const type.

swap

Exchange the value of this object with the specified other object.

Specializations

Name

Description

HashTable_HashWrapper<FUNCTOR const>

This partial specialization handles const qualified functors, that may not be stored as a mutable member in the primary template. The need to wrap such functors diminishes greatly, as there is no need to play mutable tricks to invoke the function call operator. An alternative to providing this specialization would be to skip the wrapper entirely if using a const qualified functor in a HashTable. Note that this type has a const qualified data member, so is neither assignable nor swappable.

HashTable_HashWrapper<FUNCTOR&>

This partial specialization handles const qualified functors, that may not be stored as a mutable member in the primary template. Note that the FUNCTOR type itself may be const‐qualified, so this one partial template specialization also handles const FUNCTOR& references. In order to correctly parse with the reference‐binding rules, we drop the const in front of many of the references to FUNCTOR seen in the primary template definition. Note that this type has a reference data member, so is not default constructible, assignable or swappable.

Non-Member Functions

Name

Description

swap

Swap the functor wrapped by the specified a object with the functor wrapped by the specified b object.

Created with MrDocs