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| Associative | ||||
| Unordered associative | ||||
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| Tables | ||||
| Iterator invalidation | ||||
| Member function table | ||||
| Non-member function table |
bool empty()constnoexcept; | (since C++23) | |
Checks if the underlying containers have no elements. Equivalent to:return begin()== end();.
Contents |
(none)
true if the underlying containers are empty,false otherwise.
Constant.
The following code usesempty to check if astd::flat_multimap<int,int> contains any elements:
#include <iostream>#include <flat_map>#include <utility> int main(){std::flat_multimap<int,int> numbers;std::cout<<std::boolalpha;std::cout<<"Initially, numbers.empty(): "<< numbers.empty()<<'\n'; numbers.emplace(42,13); numbers.insert(std::make_pair(13317,123));std::cout<<"After adding elements, numbers.empty(): "<< numbers.empty()<<'\n';}
Output:
Initially, numbers.empty(): trueAfter adding elements, numbers.empty(): false
| returns the number of elements (public member function)[edit] | |
(C++17) | checks whether the container is empty (function template)[edit] |
