| (1) | ||
CharT& front(); | (until C++20) | |
constexpr CharT& front(); | (since C++20) | |
| (2) | ||
const CharT& front() const; | (until C++20) | |
constexpr const CharT& front() const; | (since C++20) |
Returns reference to the first character in the string. The behavior is undefined if empty() is true.
(none).
Reference to the first character, equivalent to operator[](0).
Constant.
In libstdc++, front() is not available in C++98 mode.
#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
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 |
|
(DR*) | accesses the last character (public member function) |
|
(C++17) | accesses the first character (public member function of std::basic_string_view<CharT,Traits>) |
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