unordered_set::unordered_set

Constructs a container object.

unordered_set(
    const unordered_set& right);
explicit unordered_set(
    size_type nbuckets = N0,
    const Hash& hfn = Hash(),
    const Pred& comp = Pred(),
    const Alloc& al = Alloc());
template<class InIt>
    unordered_set(
    InIt first, InIt last,
    size_type nbuckets = N0,
    const Hash& hfn = Hash(),
    const Pred& comp = Pred(),
    const Alloc& al = Alloc());
unordered_set(
    unordered_set&& right);

Parameters

Remarks

The first constructor specifies a copy of the sequence controlled by right. The second constructor specifies an empty controlled sequence. The third constructor inserts the sequence of element values [first, last). The fourth constructor specifies a copy of the sequence by moving right.

All constructors also initialize several stored values. For the copy constructor, the values are obtained from right. Otherwise:

the minimum number of buckets is the argument nbuckets, if present; otherwise it is a default value described here as the implementation-defined value N0.

the hash function object is the argument hfn, if present; otherwise it is Hash().

the comparison function object is the argument comp, if present; otherwise it is Pred().

the allocator object is the argument al, if present; otherwise, it is Alloc().

Example 

Code

// std_tr1__unordered_set__unordered_set_construct.cpp 
// compile with: /EHsc 
#include <unordered_set> 
#include <iostream> 
 
typedef std::unordered_set<char> Myset; 
int main() 
    { 
    Myset c1; 
 
    c1.insert('a'); 
    c1.insert('b'); 
    c1.insert('c'); 
 
// display contents " [c] [b] [a]" 
    for (Myset::const_iterator it = c1.begin(); 
        it != c1.end(); ++it) 
        std::cout << " [" << *it << "]"; 
    std::cout << std::endl; 
 
    Myset c2(8, 
        std::hash<char>(), 
        std::equal_to<char>(), 
        std::allocator<std::pair<const char, int> >()); 
 
    c2.insert('d'); 
    c2.insert('e'); 
    c2.insert('f'); 
 
// display contents " [f] [e] [d]" 
    for (Myset::const_iterator it = c2.begin(); 
        it != c2.end(); ++it) 
        std::cout << " [" << *it << "]"; 
    std::cout << std::endl; 
 
    Myset c3(c1.begin(), 
        c1.end(), 
        8, 
        std::hash<char>(), 
        std::equal_to<char>(), 
        std::allocator<std::pair<const char, int> >()); 
 
// display contents " [c] [b] [a]" 
    for (Myset::const_iterator it = c3.begin(); 
        it != c3.end(); ++it) 
        std::cout << " [" << *it << "]"; 
    std::cout << std::endl; 

    Myset c4(std::move(c3));

// display contents " [c] [b] [a]" 
    for (Myset::const_iterator it = c3.begin(); 
        it != c3.end(); ++it) 
        std::cout << " [" << *it << "]"; 
    std::cout << std::endl; 
 
    return (0); 
    } 
 

Output

 [c] [b] [a]
 [f] [e] [d]
 [c] [b] [a]
 [c] [b] [a]

Requirements

Header: <unordered_set>

Namespace: std

See Also

Reference

<unordered_set>

unordered_set Class

Other Resources

<unordered_set> Members