std::basic_string<CharT,Traits,Allocator>::resize
| (1) | ||
void resize( size_type count ); |
(until C++20) | |
constexpr void resize( size_type count ); |
(since C++20) | |
| (2) | ||
void resize( size_type count, CharT ch ); |
(until C++20) | |
constexpr void resize( size_type count, CharT ch ); |
(since C++20) |
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.
Parameters
| count | - | new size of the string |
| ch | - | character to initialize the new characters with |
Return value
(none).
Exceptions
std::length_error if count > max_size(). Any exceptions thrown by corresponding Allocator.
If an exception is thrown for any reason, this function has no effect (strong exception guarantee). (since C++11).
Example
#include <iostream>
#include <iomanip>
#include <stdexcept>
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: " << quoted( long_string ) << '\n';
long_string.resize( desired_length );
std::cout << "2. After: " << quoted( long_string ) << '\n';
std::cout << "Lengthen with a given value 'a':\n"
<< "3. Before: " << quoted( short_string ) << '\n';
short_string.resize( desired_length, 'a' );
std::cout << "4. After: " << quoted( short_string ) << '\n';
std::cout << "Lengthen with char() == " << static_cast<int>(char()) << '\n'
<< "5. Before: " << 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
See also
| returns the number of characters (public member function) |
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