xtd::collections::generic::helpers::hasher< key_t > Struct Template Reference

Definition

template<typename key_t>
struct xtd::collections::generic::helpers::hasher< key_t >

Implements a function object for hashing data.

template<typename key_t>
struct hasher;

Header

#include <xtd/collections/generic/helpers/hasher>

Namespace

xtd::collections::generic::helpers

Library

xtd.core

Remarks

The unordered associative containers xtd::collections::generic::has_set, xtd::collections::generic::hash_multi_set, xtd::collections::generic::dictionary, xtd::collections::generic::multi_dictionary use specializations of the template xtd::collections::generic::helpers::hasher as the default hash function.

Examples

The following example show how to use xtd::collections::generic::helpers::hasher with std::unordered_map.

auto key_values = std::unordered_map<xtd::date_time, xtd::string, xtd::collections::generic::helpers::hasher<xtd::date_time>, xtd::collections::generic::helpers::equator<xtd::date_time>, xtd::collections::generic::helpers::allocator<xtd::collections::generic::key_value_pair<const xtd::date_time, xtd::string>>> {};
key_values.insert({{1971, 1, 5}, "Birth date"});

Public Aliases
using	argument_type
	Represents the argument type.
using	result_type
	Represents the result type.

Public Constructors
	hasher () noexcept=default
	Initializes a new instance of the hasher.
	hasher (const xtd::collections::generic::iequality_comparer< key_t > &comparer) noexcept
	Initializes a new instance of the hasher with specified comparer.

Public Operators
auto	operator() (const argument_type &key) const noexcept -> result_type
	Serves as a hash function for a specified key with a particular type (type_t).

Member Typedef Documentation

argument_type

template<typename key_t>

using xtd::collections::generic::helpers::hasher< key_t >::argument_type

Represents the argument type.

result_type

template<typename key_t>

using xtd::collections::generic::helpers::hasher< key_t >::result_type

Represents the result type.

Constructor & Destructor Documentation

hasher() [1/2]

template<typename key_t>

xtd::collections::generic::helpers::hasher< key_t >::hasher ( )

defaultnoexcept

Initializes a new instance of the hasher.

hasher() [2/2]

template<typename key_t>

xtd::collections::generic::helpers::hasher< key_t >::hasher ( const xtd::collections::generic::iequality_comparer< key_t > & comparer )

inlineexplicitnoexcept

Initializes a new instance of the hasher with specified comparer.

Parameters

comparer

A comparer used to hash the key.

Member Function Documentation

operator()()

template<typename key_t>

auto xtd::collections::generic::helpers::hasher< key_t >::operator() ( const argument_type & key ) const -> result_type

inlinenoexcept

Serves as a hash function for a specified key with a particular type (type_t).

Parameters

key	The key to hash.

Returns

A hash code for the spesified key.

Remarks

If key_t inherits from xtd::object, the xtd::object::get_hash_code method will be used; otherwise, the std::hash object function will be used.

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The documentation for this struct was generated from the following file:

• xtd.core/include/xtd/collections/generic/helpers/hasher.hpp