| CARVIEW |
Select Language
HTTP/1.1 301 Moved Permanently
Server: nginx
Date: Sat, 19 Jul 2025 10:44:02 GMT
Content-Type: text/html; charset=UTF-8
Transfer-Encoding: chunked
Connection: keep-alive
Location: /reference/vector/vector/front/
HTTP/1.1 200 OK
Server: nginx
Date: Sat, 19 Jul 2025 10:44:02 GMT
Content-Type: text/html; charset=utf-8
Transfer-Encoding: chunked
Connection: keep-alive
ETag: W/"7c1a-bUruGT83HqZlGHcSacCLw0V7MZE"
Content-Encoding: gzip
Returns a reference to the first element in the vector.
Unlike member vector::begin, which returns an iterator to this same element, this function returns a direct reference.
Calling this function on an empty container causes undefined behavior.
If the vector object is const-qualified, the function returns a const_reference. Otherwise, it returns a reference.
Member types reference and const_reference are the reference types to the elements of the container (see vector member types).
Output:
The reference returned can be used to access or modify elements. Concurrently accessing or modifying different elements is safe.
Otherwise, it causes undefined behavior.
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>
vector
- vector::~vector
- vector::vector
member functions
- vector::assign
- vector::at
- vector::back
- vector::begin
- vector::capacity
-
vector::cbeginC++11
-
vector::cendC++11
- vector::clear
-
vector::crbeginC++11
-
vector::crendC++11
-
vector::dataC++11
-
vector::emplaceC++11
-
vector::emplace_backC++11
- vector::empty
- vector::end
- vector::erase
- vector::front
- vector::get_allocator
- vector::insert
- vector::max_size
- vector::operator[]
- vector::operator=
- vector::pop_back
- vector::push_back
- vector::rbegin
- vector::rend
- vector::reserve
- vector::resize
-
vector::shrink_to_fitC++11
- vector::size
- vector::swap
non-member overloads
public member function
<vector>
std::vector::front
reference front();const_reference front() const;
Access first element
Unlike member vector::begin, which returns an iterator to this same element, this function returns a direct reference.
Calling this function on an empty container causes undefined behavior.
Parameters
noneReturn value
A reference to the first element in the vector container.If the vector object is const-qualified, the function returns a const_reference. Otherwise, it returns a reference.
Member types reference and const_reference are the reference types to the elements of the container (see vector member types).
Example
|
|
Output:
myvector.front() is now 62 |
Complexity
Constant.Iterator validity
No changes.Data races
The container is accessed (neither the const nor the non-const versions modify the container).The reference returned can be used to access or modify elements. Concurrently accessing or modifying different elements is safe.
Exception safety
If the container is not empty, the function never throws exceptions (no-throw guarantee).Otherwise, it causes undefined behavior.
See also
- vector::at
- Access element (public member function)
- vector::operator[]
- Access element (public member function)
- vector::back
- Access last element (public member function)
Home page | Privacy policy
© cplusplus.com, 2000-2025 - All rights reserved - v3.3.4s
Spotted an error? contact us
© cplusplus.com, 2000-2025 - All rights reserved - v3.3.4s
Spotted an error? contact us