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Difference between revisions of "cpp/string/basic string/pop back"

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< cpp‎ | string‎ | basic string
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{{cpp/string/basic_string/title | pop_back}}
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{{ddcl | notes={{mark since c++11}} |
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{{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.
  
 
===Parameters===
 
===Parameters===
Line 15: Line 17:
 
===Complexity===
 
===Complexity===
 
Constant.
 
Constant.
 +
 +
===Exceptions===
 +
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
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|code=
 +
#include <cassert>
 +
#include <iomanip>
 +
#include <iostream>
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#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
 +
}
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|output=
 +
Before: "Short string!"
 +
After:  "Short string"
 +
}}
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 +
===Defect reports===
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{{dr list begin}}
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{{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}}
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{{dr list end}}
  
 
===See also===
 
===See also===
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{{dsc begin}}
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{{dsc inc|cpp/string/basic_string/dsc push_back}}
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{{dsc inc|cpp/string/basic_string/dsc erase}}
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{{dsc end}}
  
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{{dcl list begin}}
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{{langlinks|de|es|fr|it|ja|pt|ru|zh}}
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{{dcl list template | cpp/string/basic_string/dcl list push_back}}
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{{dcl list end}}
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Latest revision as of 14:10, 18 October 2024

 
C++
 
Strings library
 
std::basic_string
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basic_string::pop_back
(DR*)
(C++23)
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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) [edit]
removes characters
(public member function) [edit]
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