std::multimap<Key,T,Compare,Allocator>::begin, std::multimap<Key,T,Compare,Allocator>::cbegin

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Containers library

array (C++11)

vector

deque

forward_list (C++11)

list

set

multiset

map

multimap

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

stack

queue

priority_queue

span (C++20)

 

std::multimap

Member functions

multimap::multimap

multimap::~multimap

multimap::operator=

multimap::get_allocator

Iterators

multimap::beginmultimap::cbegin (C++11)

multimap::endmultimap::cend (C++11)

multimap::rbeginmultimap::crbegin (C++11)

multimap::rendmultimap::crend (C++11)

Capacity

multimap::empty

multimap::size

multimap::max_size

Modifiers

multimap::clear

multimap::insert

multimap::emplace (C++11)

multimap::emplace_hint (C++11)

multimap::erase

multimap::swap

multimap::extract (C++17)

multimap::merge (C++17)

Lookup

multimap::count

multimap::find

multimap::contains (C++20)

multimap::equal_range

multimap::lower_bound

multimap::upper_bound

Observers

multimap::key_comp

multimap::value_comp

Non-member functions

std::swap

erase_if (C++20)

operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)

Deduction guides(C++17)

 

iterator begin();		(until C++11)
iterator begin() noexcept;		(since C++11)
const_iterator begin() const;		(until C++11)
const_iterator begin() const noexcept;		(since C++11)
const_iterator cbegin() const noexcept;		(since C++11)

Returns an iterator to the first element of the multimap.

If the multimap is empty, the returned iterator will be equal to end().

Parameters

(none)

Return value

Iterator to the first element.

Complexity

Constant.

Example

Run this code

#include <algorithm>
#include <cassert>
#include <iostream>
#include <map>
#include <string>
#include <cstddef>
 
int main()
{
    auto show_node = [](const auto& node, char ending = '\n') {
        std::cout << "{ " << node.first << ", " << node.second << " }" << ending;
    };
 
    std::multimap<std::size_t, std::string> mmap;
    assert(mmap.begin() == mmap.end());   // OK
    assert(mmap.cbegin() == mmap.cend()); // OK
 
    mmap.insert({ sizeof(long), "LONG" });
    show_node(*(mmap.cbegin()));
    assert(mmap.begin() != mmap.end());   // OK
    assert(mmap.cbegin() != mmap.cend()); // OK
    mmap.begin()->second = "long";
    show_node(*(mmap.cbegin()));
 
    mmap.insert({ sizeof(int), "int" });
    show_node(*mmap.cbegin());
 
    mmap.insert({ sizeof(short), "short" });
    show_node(*mmap.cbegin());
 
    mmap.insert({ sizeof(char), "char" });
    show_node(*mmap.cbegin());
 
    mmap.insert({{ sizeof(float), "float" }, { sizeof(double), "double" }});
 
    std::cout << "mmap = { ";
    std::for_each(mmap.cbegin(), mmap.cend(), [&](const auto& n) { show_node(n, ' '); });
    std::cout << "};\n";
}

Possible output:

{ 8, LONG }
{ 8, long }
{ 4, int }
{ 2, short }
{ 1, char }
mmap = { { 1, char } { 2, short } { 4, int } { 4, float } { 8, long } { 8, double } };

See also

end cend (C++11)

returns an iterator to the end (public member function)