unordered_set::emplace
Adds an element constructed in place.
template<class ValTy>
pair<iterator, bool> emplace(ValTy&& val);
Parameters
Parameter |
Description |
ValTy |
The in-place constructor argument type. |
val |
Value to insert. |
Remarks
The member function determines whether an element X exists in the sequence whose key has equivalent ordering to that of val. If not, it constructs such an element X with val. The function then determines the iterator where that designates X. If an insertion occurred, the function returns std::pair(where, true). Otherwise, it returns std::pair(where, false).
If an exception is thrown during the insertion of a single element, the container is left unaltered and the exception is rethrown. If an exception is thrown during the insertion of multiple elements, the container is left in a stable but unspecified state and the exception is rethrown.
Example
// std_tr1__unordered_set__unordered_set_emplace.cpp
// compile with: /EHsc
#include <unordered_set>
#include <iostream>
#include <string>
int main()
{
unordered_set< string> c1;
string str1("a");
c1.emplace(move(str1));
cout << "After the emplace insertion, c1 contains: "
<< *c1.begin() << endl;
return (0);
}
After the emplace insertion, c1 contains: a
Requirements
Header: <unordered_set>
Namespace: std