Difference between revisions of "Template:cpp/container/at"
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m (→Example: set default to `vector`) |
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int main() | int main() | ||
{ | { | ||
| − | std::{{{1|vector}}}<int{{#ifeq: {{{1|}}}|array|,6}}> data = {1, 2, 4, 5, 5, 6}; | + | std::{{{1|vector}}}<int{{#ifeq: {{{1|}}}|array|, 6}}> data = {1, 2, 4, 5, 5, 6}; |
// Set element 1 | // Set element 1 | ||
Revision as of 15:39, 2 October 2023
| reference at( size_type pos ); |
(1) | (since {std}) |
| const_reference at( size_type pos ) const; |
(2) | (since {std}) |
Returns a reference to the element at specified location pos, with bounds checking.
If pos is not within the range of the container, an exception of type std::out_of_range is thrown.
Contents |
Parameters
| pos | - | position of the element to return |
Return value
Reference to the requested element.
Exceptions
std::out_of_range if pos >= size().
Complexity
Constant.
Example
Run this code
#include <iostream> #include <vector> #include <stdexcept> #ifdef __GNUG__ [[gnu::noinline]] #endif unsigned int runtime_six() // Emulate runtime input { return 6u; } int main() { std::vector<int> data = {1, 2, 4, 5, 5, 6}; // Set element 1 data.at(1) = 88; // Read element 2 std::cout << "Element at index 2 has value " << data.at(2) << '\n'; std::cout << "data size = " << data.size() << '\n'; try { // Set element 6, where the index is determined at runtime data.at(runtime_six()) = 666; } catch (std::out_of_range const& exc) { std::cout << exc.what() << '\n'; } // Print final values std::cout << "data:"; for (int elem : data) std::cout << ' ' << elem; std::cout << '\n'; }
Possible output:
Element at index 2 has value 4 data size = 6 std::out_of_range: pos >= size() data: 1 88 4 5 5 6
See also
| access specified element (public member function of std::{{{1}}})
|
