Difference between revisions of "cpp/container/multimap/begin"
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Revision as of 11:51, 4 May 2012
| iterator begin(); |
(1) | (noexcept since C++11) |
| const_iterator begin() const; |
(2) | (noexcept since C++11) |
| const_iterator cbegin() const noexcept; |
(3) | (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().
Contents |
Parameters
(none)
Return value
Iterator to the first element.
Complexity
Constant.
Notes
libc++ backports cbegin() to C++98 mode.
Example
Run this code
#include <algorithm> #include <cassert> #include <cstddef> #include <iostream> #include <map> #include <string> 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
| (C++11) |
returns an iterator to the end (public member function) |
| (C++11)(C++14) |
returns an iterator to the beginning of a container or array (function template) |
