Difference between revisions of "cpp/string/basic string/at"
From cppreference.com
< cpp | string | basic string
m (→See also: + crosslink) |
m (→Synopsis: added numbering for overloads, IMfO, this should always be done, even if explanation part does not use the numbers.) |
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| Line 1: | Line 1: | ||
| − | {{cpp/string/basic_string/title | at}} | + | {{cpp/string/basic_string/title|at}} |
{{cpp/string/basic_string/navbar}} | {{cpp/string/basic_string/navbar}} | ||
{{dcl begin}} | {{dcl begin}} | ||
| − | {{dcl rev multi | + | {{dcl rev multi|num=1|until1=c++20 |
| − | | until1=c++20 | dcl1= | + | |dcl1= |
| − | reference | + | reference at( size_type pos ); |
| − | | dcl2= | + | |dcl2= |
| − | constexpr reference | + | constexpr reference at( size_type pos ); |
}} | }} | ||
| − | {{dcl rev multi | + | {{dcl rev multi|num=2|until1=c++20 |
| − | | until1=c++20 | dcl1= | + | |dcl1= |
const_reference at( size_type pos ) const; | const_reference at( size_type pos ) const; | ||
| − | | dcl2= | + | |dcl2= |
constexpr const_reference at( size_type pos ) const; | constexpr const_reference at( size_type pos ) const; | ||
}} | }} | ||
| Line 20: | Line 20: | ||
===Parameters=== | ===Parameters=== | ||
{{par begin}} | {{par begin}} | ||
| − | {{par | pos | position of the character to return}} | + | {{par|pos|position of the character to return}} |
{{par end}} | {{par end}} | ||
| Line 34: | Line 34: | ||
===Example=== | ===Example=== | ||
{{example | {{example | ||
| − | | code= | + | |code= |
| − | + | ||
#include <iostream> | #include <iostream> | ||
| + | #include <stdexcept> | ||
#include <string> | #include <string> | ||
| Line 50: | Line 50: | ||
std::cout << "string capacity = " << s.capacity() << '\n'; | std::cout << "string capacity = " << s.capacity() << '\n'; | ||
| − | try { | + | try |
| + | { | ||
// This will throw since the requested offset is greater than the current size. | // This will throw since the requested offset is greater than the current size. | ||
s.at(3) = 'x'; | s.at(3) = 'x'; | ||
} | } | ||
| − | catch (std::out_of_range const& exc) { | + | catch (std::out_of_range const& exc) |
| + | { | ||
std::cout << exc.what() << '\n'; | std::cout << exc.what() << '\n'; | ||
} | } | ||
} | } | ||
| − | | p=true | + | |p=true |
| − | | output= | + | |output= |
abx | abx | ||
string size = 3 | string size = 3 | ||
| Line 69: | Line 71: | ||
{{dsc begin}} | {{dsc begin}} | ||
| − | {{dsc inc | cpp/string/basic_string/dsc operator_at }} | + | {{dsc inc|cpp/string/basic_string/dsc operator_at}} |
| − | {{dsc inc | cpp/string/basic_string_view/dsc {{SUBPAGENAMEE}}}} | + | {{dsc inc|cpp/string/basic_string_view/dsc {{SUBPAGENAMEE}}}} |
{{dsc end}} | {{dsc end}} | ||
{{langlinks|de|es|fr|it|ja|pl|pt|ru|zh}} | {{langlinks|de|es|fr|it|ja|pl|pt|ru|zh}} | ||
Revision as of 05:56, 25 March 2023
| (1) | ||
reference at( size_type pos ); |
(until C++20) | |
| constexpr reference at( size_type pos ); |
(since C++20) | |
| (2) | ||
const_reference at( size_type pos ) const; |
(until C++20) | |
| constexpr const_reference at( size_type pos ) const; |
(since C++20) | |
Returns a reference to the character at specified location pos. Bounds checking is performed, exception of type std::out_of_range will be thrown on invalid access.
Contents |
Parameters
| pos | - | position of the character to return |
Return value
Reference to the requested character.
Exceptions
Throws std::out_of_range if pos >= size().
Complexity
Constant.
Example
Run this code
#include <iostream> #include <stdexcept> #include <string> int main() { std::string s("message"); // for capacity s = "abc"; s.at(2) = 'x'; // ok std::cout << s << '\n'; std::cout << "string size = " << s.size() << '\n'; std::cout << "string capacity = " << s.capacity() << '\n'; try { // This will throw since the requested offset is greater than the current size. s.at(3) = 'x'; } catch (std::out_of_range const& exc) { std::cout << exc.what() << '\n'; } }
Possible output:
abx string size = 3 string capacity = 7 basic_string::at
See also
| accesses the specified character (public member function) | |
| accesses the specified character with bounds checking (public member function of std::basic_string_view<CharT,Traits>)
|
