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

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< cpp‎ | string‎ | basic string
(Added (C++11) mark again, as it was also done in navbar, despite DR534. Is this correct?.)
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CharT& front();
 
CharT& front();
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|since2=c++20|dcl2=
 
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constexpr CharT& front();
 
 
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const CharT& front() const;
 
const CharT& front() const;
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constexpr const CharT& front() const;
 
 
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===Complexity===
 
===Complexity===
 
Constant.
 
Constant.
 +
 +
===Notes===
 +
In libstdc++, {{tt|front()}} is [https://gcc.gnu.org/onlinedocs/libstdc++/manual/strings.html#strings.string.shrink not available] in C++98 mode.
  
 
===Example===
 
===Example===

Latest revision as of 05:43, 22 April 2024

 
C++
 
Strings library
 
std::basic_string
Member functions
(C++23)
Element access
basic_string::front
(DR*)
(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& front();
 (1) (constexpr since C++20)
const CharT& front() const;
 (2) (constexpr since C++20)

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

Contents

[edit] Parameters

(none)

[edit] Return value

Reference to the first character, equivalent to operator[](0).

[edit] Complexity

Constant.

[edit] Notes

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

[edit] Example

Run this code
#include <iostream>
#include <string>
 
int main()
{
    std::string s("Exemplary");
    char& f1 = s.front();
    f1 = 'e';
    std::cout << s << '\n'; // "exemplary"
 
    std::string const c("Exemplary");
    char const& f2 = c.front();
    std::cout << &f2 << '\n'; // "Exemplary"
}

Output: 

exemplary
Exemplary

[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 front() added

[edit] See also

(DR*)
 accesses the last character
(public member function) [edit]
accesses the first character
(public member function of std::basic_string_view<CharT,Traits>) [edit]
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