| CARVIEW |
Select Language
HTTP/1.1 301 Moved Permanently
Server: nginx
Date: Sat, 19 Jul 2025 14:36:45 GMT
Content-Type: text/html; charset=UTF-8
Transfer-Encoding: chunked
Connection: keep-alive
Location: /reference/vector/vector/at/
HTTP/1.1 200 OK
Server: nginx
Date: Sat, 19 Jul 2025 14:36:45 GMT
Content-Type: text/html; charset=utf-8
Transfer-Encoding: chunked
Connection: keep-alive
ETag: W/"7eca-T8hNwtFATACWkgMTJl4GZEQYwYw"
Content-Encoding: gzip
Returns a reference to the element at position n in the vector.
The function automatically checks whether n is within the bounds of valid elements in the vector, throwing an out_of_range exception if it is not (i.e., if n is greater than, or equal to, its size). This is in contrast with member operator[], that does not check against bounds.
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.
It throws out_of_range if n is out of bounds.
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::at
reference at (size_type n);const_reference at (size_type n) const;
Access element
The function automatically checks whether n is within the bounds of valid elements in the vector, throwing an out_of_range exception if it is not (i.e., if n is greater than, or equal to, its size). This is in contrast with member operator[], that does not check against bounds.
Parameters
- n
- Position of an element in the container.
If this is greater than, or equal to, the vector size, an exception of type out_of_range is thrown.
Notice that the first element has a position of 0 (not 1).
Member type size_type is an unsigned integral type.
Return value
The element at the specified position in the 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 contains: 0 1 2 3 4 5 6 7 8 9 |
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
Strong guarantee: if an exception is thrown, there are no changes in the container.It throws out_of_range if n is out of bounds.
See also
- vector::operator[]
- Access element (public member function)
- vector::front
- Access first 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