Difference between revisions of "cpp/string/basic string/pop back"
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< cpp | string | basic string
m (Add simple example) |
m ({{ddcla}}) |
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| − | {{cpp/string/basic_string/title | pop_back}} | + | {{cpp/string/basic_string/title|pop_back}} |
{{cpp/string/basic_string/navbar}} | {{cpp/string/basic_string/navbar}} | ||
| − | {{ | + | {{ddcla|constexpr=c++20| |
| − | + | ||
| − | | | + | |
void pop_back(); | void pop_back(); | ||
| − | |||
| − | |||
}} | }} | ||
| − | |||
Removes the last character from the string. | Removes the last character from the string. | ||
| − | Equivalent to {{c|erase(end()-1)}}. The behavior is undefined if the string is empty. | + | Equivalent to {{c|erase(end() - 1)}}. The behavior is undefined if the string is empty. |
===Parameters=== | ===Parameters=== | ||
| Line 25: | Line 20: | ||
===Exceptions=== | ===Exceptions=== | ||
Throws nothing. | Throws nothing. | ||
| + | |||
| + | ===Notes=== | ||
| + | In libstdc++, {{tt|pop_back()}} is [https://gcc.gnu.org/onlinedocs/libstdc++/manual/strings.html#strings.string.shrink not available] in C++98 mode. | ||
===Example=== | ===Example=== | ||
{{example | {{example | ||
| − | | code= | + | |code= |
#include <cassert> | #include <cassert> | ||
| − | #include < | + | #include <iomanip> |
#include <iostream> | #include <iostream> | ||
| − | + | #include <string> | |
| + | |||
int main() | int main() | ||
{ | { | ||
| − | std::string str("Short string"); | + | std::string str("Short string!"); |
| − | std::cout << " | + | std::cout << "Before: " << std::quoted(str) << '\n'; |
| − | assert(str.size() == | + | assert(str.size() == 13); |
| − | + | ||
str.pop_back(); | str.pop_back(); | ||
| − | std::cout << " | + | std::cout << "After: " << std::quoted(str) << '\n'; |
| − | assert(str.size() == | + | assert(str.size() == 12); |
| + | |||
| + | str.clear(); | ||
| + | // str.pop_back(); // undefined behavior | ||
} | } | ||
| − | + | |output= | |
| − | + | Before: "Short string!" | |
| − | + | After: "Short string" | |
}} | }} | ||
| − | === | + | ===Defect reports=== |
| + | {{dr list begin}} | ||
| + | {{dr list item|wg=lwg|dr=534|std=C++98|before={{lc|std::basic_string}} did not have the member function {{tt|pop_back()}}|after=added}} | ||
| + | {{dr list end}} | ||
| + | ===See also=== | ||
{{dsc begin}} | {{dsc begin}} | ||
| − | {{dsc inc | cpp/string/basic_string/dsc push_back}} | + | {{dsc inc|cpp/string/basic_string/dsc push_back}} |
| − | {{dsc inc | cpp/string/basic_string/dsc erase}} | + | {{dsc inc|cpp/string/basic_string/dsc erase}} |
{{dsc end}} | {{dsc end}} | ||
{{langlinks|de|es|fr|it|ja|pt|ru|zh}} | {{langlinks|de|es|fr|it|ja|pt|ru|zh}} | ||
Latest revision as of 14:10, 18 October 2024
void pop_back(); |
(constexpr since C++20) | |
Removes the last character from the string.
Equivalent to erase(end() - 1). The behavior is undefined if the string is empty.
Contents |
[edit] Parameters
(none)
[edit] Return value
(none)
[edit] Complexity
Constant.
[edit] Exceptions
Throws nothing.
[edit] Notes
In libstdc++, pop_back() is not available in C++98 mode.
[edit] Example
Run this code
#include <cassert> #include <iomanip> #include <iostream> #include <string> int main() { std::string str("Short string!"); std::cout << "Before: " << std::quoted(str) << '\n'; assert(str.size() == 13); str.pop_back(); std::cout << "After: " << std::quoted(str) << '\n'; assert(str.size() == 12); str.clear(); // str.pop_back(); // undefined behavior }
Output:
Before: "Short string!" After: "Short string"
[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 534 | C++98 | std::basic_string did not have the member function pop_back()
|
added |
[edit] See also
| appends a character to the end (public member function) | |
| removes characters (public member function) |
