std::basic_string::basic_string

(1) empty string constructor (default constructor)

Constructs an empty string, with a length of zero characters.

(2) copy constructors

Constructs a copy of str.

(3) substring constructor

Copies the portion of str that begins at the character position pos and spans len characters (or until the end of str, if either str is too short or if len is basic_string::npos).

(4) from c-string

Copies the null-terminated character sequence (C-string) pointed by s.
The length is determined by calling traits_type::length(s).

(5) from buffer

Copies the first n characters from the array of characters pointed by s.

(6) fill constructor

Fills the string with n consecutive copies of character c.

(7) range constructor

Copies the sequence of characters in the range [first,last), in the same order.

(8) initializer list

Copies each of the characters in il, in the same order.

(9) move contructors

Acquires the contents of str.
str is left in an unspecified but valid state.

Parameters

alloc

Allocator object.
The container keeps and uses an internal copy of this allocator.
Member type allocator_type is the internal allocator type used by the container, defined in basic_string as an alias of its third template parameter (Alloc).
If allocator_type is an instantiation of the default allocator (which has no state), this is not relevant.

str

Another basic_string object of the same type (with the same class template arguments charT, traits and Alloc), whose value is either copied or acquired.

pos

Position of the first character in str that is copied to the object as a substring.
If this is greater than str's length, it throws out_of_range.
Note: The first character in str is denoted by a value of 0 (not 1).

len

Length of the substring to be copied (if the string is shorter, as many characters as possible are copied).
A value of basic_string::npos indicates all characters until the end of str.

s

Pointer to an array of characters (such as a c-string).

n

Number of characters to copy.

c

Character to fill the string with. Each of the n characters in the string will be initialized to a copy of this value.

first, last

Input iterators to the initial and final positions in a range. The range used is [first,last), which includes all the characters between first and last, including the character pointed by first but not the character pointed by last.
The function template argument InputIterator shall be an input iterator type that points to elements of a type convertible to charT.
If InputIterator is an integral type, the arguments are casted to the proper types so that signature (5) is used instead.

il

An initializer_list object.
These objects are automatically constructed from initializer list declarators.

Example

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23

// string constructor
#include <iostream>
#include <string>

int main ()
{
  std::string s0 ("Initial string");

  // constructors used in the same order as described above:
  std::string s1;
  std::string s2 (s0);
  std::string s3 (s0, 8, 3);
  std::string s4 ("A character sequence", 6);
  std::string s5 ("Another character sequence");
  std::string s6 (10, 'x');
  std::string s7a (10, 42);
  std::string s7b (s0.begin(), s0.begin()+7);

  std::cout << "s1: " << s1 << "\ns2: " << s2 << "\ns3: " << s3;
  std::cout << "\ns4: " << s4 << "\ns5: " << s5 << "\ns6: " << s6;
  std::cout << "\ns7a: " << s7a << "\ns7b: " << s7b << '\n';
  return 0;
}

s1: 
s2: Initial string
s3: str
s4: A char
s5: Another character sequence
s6: xxxxxxxxxx
s7a: **********
s7b: Initial

Complexity

Iterator validity

Data races

Exception safety

See also

basic_string::operator=

String assignment (public member function)

basic_string::assign

Assign content to string (public member function)

basic_string::resize

Resize string (public member function)

basic_string::clear

Clear string (public member function)