Namespaces
Variants
Views
Actions

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

From cppreference.com
< cpp‎ | string‎ | basic string
(Created page with "{{cpp/string/basic_string/title | back}} {{cpp/string/basic_string/sidebar}} {{ddcl list begin}} {{ddcl list item | notes={{mark c++0x}} | CharT& back(); }} {{ddcl list item | no...")
 
m (→‎Synopsis: +constexpr since)
 
(27 intermediate revisions by 11 users not shown)
Line 1: Line 1:
−
{{cpp/string/basic_string/title | back}}
+
{{cpp/string/basic_string/title|back}}
−
{{cpp/string/basic_string/sidebar}}
+
{{cpp/string/basic_string/navbar}}
−
{{ddcl list begin}}
+
{{dcl begin}}
−
{{ddcl list item | notes={{mark c++0x}} |
+
{{dcl|num=1|notes={{mark constexpr since c++20}}|
 
CharT& back();
 
CharT& back();
 
}}
 
}}
−
{{ddcl list item | notes={{mark c++0x}} |
+
{{dcl|num=2|notes={{mark constexpr since c++20}}|
 
const CharT& back() const;
 
const CharT& back() const;
 
}}
 
}}
−
{{ddcl list end}}
+
{{dcl end}}
  
−
Returns reference to the last character in the string.  
+
Returns reference to the last character in the string. The behavior is undefined if {{lc|empty()}} is {{c/core|true}}.
  
−
<!-- ======== -->
+
===Parameters===
−
{{params}}
+
(none)
−
{{param none}}
+
  
−
<!-- ======== -->
+
===Return value===
−
{{returns}}
+
Reference to the last character, equivalent to {{c|operator[](size() - 1)}}.
  
−
reference to the last character.
+
===Complexity===
 +
Constant.
  
−
<!-- ======== -->
+
===Notes===
−
{{complex}}
+
In libstdc++, {{tt|back()}} is [https://gcc.gnu.org/onlinedocs/libstdc++/manual/strings.html#strings.string.shrink not available] in C++98 mode.
−
{{complex constant}}
+
  
−
<!-- ======== -->
+
===Example===
−
{{see also}}
+
{{example
 +
|code=
 +
#include <iostream>
 +
#include <string>
  
−
{{dcl list begin}}
+
int main()
−
{{dcl list template | cpp/string/basic_string/dcl list front}}
+
{
−
{{dcl list end}}
+
    std::string s("Exemplary");
 +
    char& back1 = s.back();
 +
    back1 = 's';
 +
    std::cout << s << '\n'; // "Exemplars"
 +
   
 +
    std::string const c("Exemplary");
 +
    char const& back2 = c.back();
 +
    std::cout << back2 << '\n'; // 'y'
 +
}
 +
|output=
 +
Exemplars
 +
y
 +
}}
 +
 
 +
===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|back()}}|after=added}}
 +
{{dr list end}}
 +
 
 +
===See also===
 +
{{dsc begin}}
 +
{{dsc inc|cpp/string/basic_string/dsc front}}
 +
{{dsc inc|cpp/string/basic_string_view/dsc {{SUBPAGENAMEE}}}}
 +
{{dsc end}}
 +
 
 +
{{langlinks|de|es|fr|it|ja|pt|ru|zh}}

Latest revision as of 05:42, 22 April 2024

 
C++
 
Strings library
 
std::basic_string
Member functions
(C++23)
Element access
(DR*)
basic_string::back
(DR*)
(C++17)
Iterators
(C++11)
(C++11)
(C++11)
(C++11)
Capacity
(DR*)
Modifiers
(C++23)
(DR*)
(C++23)
(C++23)
(C++23)  
Search
Operations
(C++20)
(C++20)
(C++23)
Constants
Non-member functions
(C++20)(C++20)
I/O
Comparison
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)
Numeric conversions
(C++11)(C++11)(C++11)
(C++11)(C++11)
(C++11)(C++11)(C++11)
(C++11)
(C++11)
Literals
(C++14)
Helper classes
(C++11)
Deduction guides (C++17)

 
CharT& back();
 (1) (constexpr since C++20)
const CharT& back() const;
 (2) (constexpr since C++20)

Returns reference to the last character in the string. The behavior is undefined if empty() is true.

Contents

[edit] Parameters

(none)

[edit] Return value

Reference to the last character, equivalent to operator[](size() - 1).

[edit] Complexity

Constant.

[edit] Notes

In libstdc++, back() is not available in C++98 mode.

[edit] Example

Run this code
#include <iostream>
#include <string>
 
int main()
{
    std::string s("Exemplary");
    char& back1 = s.back();
    back1 = 's';
    std::cout << s << '\n'; // "Exemplars"
 
    std::string const c("Exemplary");
    char const& back2 = c.back();
    std::cout << back2 << '\n'; // 'y'
}

Output: 

Exemplars
y

[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 back() added

[edit] See also

(DR*)
 accesses the first character
(public member function) [edit]
accesses the last character
(public member function of std::basic_string_view<CharT,Traits>) [edit]
Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/string/basic_string/back&oldid=171124"