std::basic_string::basic_string

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Strings library

Null-terminated strings

Byte strings

Multibyte strings

Wide strings

Classes

basic_string

char_traits

 

std::basic_string

Member functions basic_string::basic_string basic_string::operator= basic_string::assign basic_string::get_allocator Element access basic_string::at basic_string::operator[] basic_string::front (C++11) basic_string::back (C++11) basic_string::data basic_string::c_str Iterators basic_string::beginbasic_string::cbegin (C++11) basic_string::endbasic_string::cend (C++11) basic_string::rbeginbasic_string::crbegin (C++11) basic_string::rendbasic_string::crend (C++11) Capacity basic_string::empty basic_string::sizebasic_string::length basic_string::max_size basic_string::reserve basic_string::capacity basic_string::shrink_to_fit (C++11)

Operations basic_string::clear basic_string::insert basic_string::erase basic_string::push_back basic_string::pop_back (C++11) basic_string::append basic_string::operator+= basic_string::compare basic_string::replace basic_string::substr basic_string::copy basic_string::resize basic_string::swap Search basic_string::find basic_string::rfind basic_string::find_first_of basic_string::find_first_not_of basic_string::find_last_of basic_string::find_last_not_of Constants basic_string::npos

Non-member functions operator+ operator==operator!=operator<operator>operator<=operator>= swap(std::basic_string) operator<<operator>> getline stoistolstoll (C++11)(C++11)(C++11) stoulstoull (C++11)(C++11) stofstodstold (C++11)(C++11)(C++11) to_string (C++11) to_wstring (C++11) Helper classes hash<std::string>hash<std::wstring>hash<std::u32string>hash<std::u16string> (C++11)(C++11)(C++11)(C++11)

 

	(1)
explicit basic_string( const Allocator& alloc = Allocator() );			(until C++14)
basic_string() : basic_string( Allocator() ) {} explicit basic_string( const Allocator& alloc );			(since C++14)
basic_string( size_type count,               CharT ch,               const Allocator& alloc = Allocator() );		(2)
basic_string( const basic_string& other,               size_type pos,               size_type count = std::basic_string::npos,               const Allocator& alloc = Allocator() );		(3)
basic_string( const CharT* s,               size_type count,               const Allocator& alloc = Allocator() );		(4)
basic_string( const CharT* s,               const Allocator& alloc = Allocator() );		(5)
template< class InputIt > basic_string( InputIt first, InputIt last,               const Allocator& alloc = Allocator() );		(6)
basic_string( const basic_string& other );		(7)
basic_string( const basic_string& other, const Allocator& alloc );		(7)	(since C++11)
basic_string( basic_string&& other );		(8)	(since C++11)
basic_string( basic_string&& other, const Allocator& alloc );		(8)	(since C++11)
basic_string( std::initializer_list<CharT> init,               const Allocator& alloc = Allocator() );		(9)	(since C++11)

Constructs new string from a variety of data sources and optionally using user supplied allocator alloc.

1) Default constructor. Constructs empty string (zero size and unspecified capacity)

2) Constructs the string with count copies of character ch. The behavior is undefined if count >= npos

3) Constructs the string with a substring [pos, pos+count) of other. If the requested substring lasts past the end of the string, or if count == npos, the resulting substring is [pos, size()).

4) Constructs the string with the first count characters of character string pointed to by s. s can contain null characters. The behavior is undefined if s does not point at an array of at least count elements of CharT.

5) Constructs the string with the contents initialized with a copy of the null-terminated character string pointed to by s. The length of the string is determined by the first null character. The behavior is undefined if s does not point at an array of at least Traits::length(s)+1 elements of CharT.

6) Constructs the string with the contents of the range [first, last).

This overload has the same effect as overload (2) if InputIt is an integral type.	(until C++11)
This overload only participates in overload resolution if InputIt satisfies InputIterator.	(since C++11)

7) Copy constructor. Constructs the string with the copy of the contents of other.

8) Move constructor. Constructs the string with the contents of other using move semantics. other is left in valid, but unspecified state.

9) Constructs the string with the contents of the initializer list init.

Parameters

alloc	-	allocator to use for all memory allocations of this string
count	-	size of the resulting string
ch	-	value to initialize the string with
first, last	-	range to copy the characters from
s	-	pointer to a character string to use as source to initialize the string with
other	-	another string to use as source to initialize the string with
init	-	initializer list to initialize the string with

Complexity

1) constant

2-4) linear in count

5) linear in length of s

6) linear in distance between first and last

7) linear in size of other

8) constant. If alloc is given and alloc != other.get_allocator(), then linear

9) linear in size of init

Exceptions

1) noexcept specification:   noexcept(noexcept(Allocator()))

(since C++17)

3) std::out_of_range if pos > other.size()

8) Throws nothing if alloc == str.get_allocator()	(until C++14)
8) noexcept specification:   noexcept	(since C++14)

Example

Run this code

#include <iostream>
#include <cassert>
#include <iterator>
#include <string>
 
int main()
{
  {
    // string::string()
    std::string s;
    assert(s.empty() && (s.length() == 0) && (s.size() == 0));
  }
 
  {
    // string::string(size_type count, charT ch)
    std::string s(4, '=');
    std::cout << s << '\n'; // "===="
  }
 
  {
    std::string const other("Exemplary");
    // string::string(string const& other, size_type pos, size_type count)
    std::string s(other, 0, other.length()-1);
    std::cout << s << '\n'; // "Exemplar"
  }
 
  {
    // string::string(charT const* s, size_type count)
    std::string s("C-style string", 7);
    std::cout << s << '\n'; // "C-style"
  }
 
  {
    // string::string(charT const* s)
    std::string s("C-style\0string");
    std::cout << s << '\n'; // "C-style"
  }
 
  {
    char mutable_c_str[] = "another C-style string";
    // string::string(InputIt first, InputIt last)
    std::string s(std::begin(mutable_c_str)+8, std::end(mutable_c_str)-1);
    std::cout << s << '\n'; // "C-style string"
  }
 
  {
    std::string const other("Exemplar");
    std::string s(other);
    std::cout << s << '\n'; // "Exemplar"
  }
 
  {
    // string::string(string&& str)
    std::string s(std::string("C++ by ") + std::string("example"));
    std::cout << s << '\n'; // "C++ by example"
  }
 
  {
    // string(std::initializer_list<charT> ilist)
    std::string s({ 'C', '-', 's', 't', 'y', 'l', 'e' });
    std::cout << s << '\n'; // "C-style"
  }
}

Output:

====
Exemplar
C-style
C-style
C-style string
Exemplar
C++ by example
C-style

See also

assign	assign characters to a string (public member function)
operator=	assigns values to the string (public member function)