std::basic_string<CharT,Traits,Allocator>::resize - cppreference.com (original) (raw)

Resizes the string to contain count characters.

If the current size is less than count, additional characters are appended:

1. Initializes appended characters to CharT() ('\0' if CharT is char).

2. Initializes appended characters to ch.

If the current size is greater than count, the string is reduced to its first count elements.

[edit] Parameters

[edit] Exceptions

std::length_error if count > max_size() is true. Any exceptions thrown by corresponding Allocator.

If an exception is thrown for any reason, this function has no effect (strong exception safety guarantee).

[edit] Example

#include #include #include   int main() { const unsigned desired_length{8}; std::string long_string("Where is the end?"); std::string short_string("H");   std::cout << "Basic functionality:\n" << "Shorten:\n" << "1. Before: " << std::quoted(long_string) << '\n'; long_string.resize(desired_length); std::cout << "2. After: " << std::quoted(long_string) << '\n';   std::cout << "Lengthen with a given value 'a':\n" << "3. Before: " << std::quoted(short_string) << '\n'; short_string.resize(desired_length, 'a'); std::cout << "4. After: " << std::quoted(short_string) << '\n';   std::cout << "Lengthen with char() == " << static_cast(char()) << '\n' << "5. Before: " << std::quoted(short_string) << '\n'; short_string.resize(desired_length + 3); std::cout << "6. After: ""; for (char c : short_string) std::cout << (c == char() ? '@' : c); std::cout << ""\n\n";   std::cout << "Errors:\n"; std::string s;   try { // size is OK, no length_error // (may throw bad_alloc) s.resize(s.max_size() - 1, 'x'); } catch (const std::bad_alloc& ex) { std::cout << "1. Exception: " << ex.what() << '\n'; }   try { // size is OK, no length_error // (may throw bad_alloc) s.resize(s.max_size(), 'x'); } catch (const std::bad_alloc& ex) { std::cout << "2. Exception: " << ex.what() << '\n'; }   try { // size is BAD, throw length_error s.resize(s.max_size() + 1, 'x'); } catch (const std::length_error& ex) { std::cout << "3. Length error: " << ex.what() << '\n'; } }

Possible output:

Basic functionality: Shorten:

1. Before: "Where is the end?"
2. After: "Where is" Lengthen with a given value 'a':
3. Before: "H"
4. After: "Haaaaaaa" Lengthen with char() == 0
5. Before: "Haaaaaaa"
6. After: "Haaaaaaa@@@"

  Errors:

1. Exception: std::bad_alloc
2. Exception: std::bad_alloc
3. Length error: basic_string::_M_replace_aux

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit] See also