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std::map<Key,T,Compare,Allocator>::value_compare

class value_compare;

std::map::value_compare is a function object that compares objects of type std::map::value_type (key-value pairs) by comparing of the first components of the pairs.

Member types

Type	Definition
`result_type` (deprecated in C++17)(removed in C++20)	`bool`
`first_argument_type` (deprecated in C++17)(removed in C++20)	`value_type`
`second_argument_type` (deprecated in C++17)(removed in C++20)	`value_type`

These member types are obtained via publicly inheriting std::binary_function<value_type, value_type, bool>.

(until C++11)

Protected member objects

Compare comp

the stored comparator
(protected member object)

Member functions

(constructor)	constructs a new `value_compare` object (protected member function)
operator()	compares two values of type `value_type` (public member function)

std::map<Key,T,Compare,Alloc>::value_compare::value_compare

protected:
value_compare( Compare c );

Initializes the internal instance of the comparator to c.

Parameters

comparator to assign

std::map<Key,T,Compare,Alloc>::value_compare::operator()

bool operator()( const value_type& lhs, const value_type& rhs ) const;

Compares lhs.first and rhs.first by calling the stored comparator.

Parameters

lhs, rhs

values to compare

Return value

comp(lhs.first, rhs.first).

Exceptions

May throw implementation-defined exceptions.

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