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| Deduction guides(C++17) | ||||||
bool empty()constnoexcept; | (since C++11) (constexpr since C++26) | |
Checks if the container has no elements.
Contents |
true if the container is empty,false otherwise.
Constant.
The following code usesempty to check if astd::unordered_map<int,int> contains any elements:
#include <iostream>#include <unordered_map>#include <utility> int main(){std::unordered_map<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] |
