constexpr bool empty() const noexcept; | (since C++17) (until C++20) | |
[[nodiscard]] constexpr bool empty() const noexcept; | (since C++20) |
Checks if the view has no characters, i.e. whether size() == 0.
(none).
true if the view is empty, false otherwise.
Constant.
#include <iostream>
#include <string_view>
// Print a string surrounded by single quotes, its
// length and whether it is considered empty.
void check_string(std::string_view ref)
{
std::cout << std::boolalpha
<< "'" << ref << "' has " << ref.size()
<< " character(s); emptiness: " << ref.empty() << '\n';
}
int main(int argc, char **argv)
{
// An empty string
check_string("");
// Almost always not empty: argv[0]
if (argc > 0)
check_string(argv[0]);
}Possible output:
'' has 0 character(s); emptiness: true './a.out' has 7 character(s); emptiness: false
|
(C++17) | returns the number of characters (public member function) |
|
(C++17) | returns the maximum number of characters (public member function) |
|
(C++17)(C++20) | returns the size of a container or array (function template) |
|
(C++17) | checks whether the container is empty (function template) |
| checks whether the string is empty (public member function of std::basic_string<CharT,Traits,Allocator>) |
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