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Returns whether the map container is empty (i.e. whether its size is 0).
This function does not modify the container in any way. To clear the content of a map container, see map::clear.
Output:
No contained elements are accessed: concurrently accessing or modifying them is safe.
Reference
C library:
- <cassert> (assert.h)
- <cctype> (ctype.h)
- <cerrno> (errno.h)
-
<cfenv> (fenv.h)C++11
- <cfloat> (float.h)
-
<cinttypes> (inttypes.h)C++11
- <ciso646> (iso646.h)
- <climits> (limits.h)
- <clocale> (locale.h)
- <cmath> (math.h)
- <csetjmp> (setjmp.h)
- <csignal> (signal.h)
- <cstdarg> (stdarg.h)
-
<cstdbool> (stdbool.h)C++11
- <cstddef> (stddef.h)
-
<cstdint> (stdint.h)C++11
- <cstdio> (stdio.h)
- <cstdlib> (stdlib.h)
- <cstring> (string.h)
-
<ctgmath> (tgmath.h)C++11
- <ctime> (time.h)
-
<cuchar> (uchar.h)C++11
- <cwchar> (wchar.h)
- <cwctype> (wctype.h)
Containers:
-
<array>C++11
- <deque>
-
<forward_list>C++11
- <list>
- <map>
- <queue>
- <set>
- <stack>
-
<unordered_map>C++11
-
<unordered_set>C++11
- <vector>
-
Input/Output:
Multi-threading:
-
<atomic>C++11
-
<condition_variable>C++11
-
<future>C++11
-
<mutex>C++11
-
<thread>C++11
-
Other:
- <algorithm>
- <bitset>
-
<chrono>C++11
-
<codecvt>C++11
- <complex>
- <exception>
- <functional>
-
<initializer_list>C++11
- <iterator>
- <limits>
- <locale>
- <memory>
- <new>
- <numeric>
-
<random>C++11
-
<ratio>C++11
-
<regex>C++11
- <stdexcept>
- <string>
-
<system_error>C++11
-
<tuple>C++11
-
<type_traits>C++11
-
<typeindex>C++11
- <typeinfo>
- <utility>
- <valarray>
map
- map::~map
- map::map
member functions
-
map::atC++11
- map::begin
-
map::cbeginC++11
-
map::cendC++11
- map::clear
- map::count
-
map::crbeginC++11
-
map::crendC++11
-
map::emplaceC++11
-
map::emplace_hintC++11
- map::empty
- map::end
- map::equal_range
- map::erase
- map::find
- map::get_allocator
- map::insert
- map::key_comp
- map::lower_bound
- map::max_size
- map::operator[]
- map::operator=
- map::rbegin
- map::rend
- map::size
- map::swap
- map::upper_bound
- map::value_comp
-
non-member overloads
public member function
<map>
std::map::empty
bool empty() const;
bool empty() const noexcept;
Test whether container is empty
This function does not modify the container in any way. To clear the content of a map container, see map::clear.
Parameters
noneReturn Value
true if the container size is 0, false otherwise.Example
|
|
Output:
a => 10 b => 20 c => 30 |
Complexity
Constant.Iterator validity
No changes.Data races
The container is accessed.No contained elements are accessed: concurrently accessing or modifying them is safe.
Exception safety
No-throw guarantee: this member function never throws exceptions.See also
- map::clear
- Clear content (public member function)
- map::erase
- Erase elements (public member function)
- map::size
- Return container size (public member function)
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© cplusplus.com, 2000-2025 - All rights reserved - v3.3.4s
Spotted an error? contact us