basic_string::basic_string

Constructs a string that is empty or initialized by specific characters, or that is a copy of all or part of some other string object or C-string.

basic_string(
   const value_type* _Ptr, 
   size_type _Count, 
   const allocator_type& _Al = Allocator ( )
); 
basic_string(
   const value_type* _Ptr, 
   const allocator_type& _Al = Allocator ( )
); 
basic_string(
   const basic_string& _Right, 
   size_type _Roff, 
   size_type _Count = npos,
   const allocator_type& _Al = Allocator ( )
);
basic_string(
   size_type _Count,
   value_type _Ch,
   const allocator_type& _Al = Allocator ( )
);
explicit basic_string(
   const allocator_type& _Al = Allocator ( )
);
template<class _It>
      basic_string(
            _It _First,
            _It _Last,
            const allocator_type& _Al = Allocator ( )
);
basic_string(
      const_pointer _First,
     const_pointer _Last
);
basic_string(
      const_iterator _First,
     const_iterator _Last
);

Parameters

_Ptr
The C-string whose characters are to be used to initialize the string being constructed. This value cannot be a null pointer.
_Al
The storage allocator class to be used for the string object being constructed, which defaults to Allocator.
_Count
The number of characters to be initialized.
_Right
The string whose characters are to be used to initialize the string being constructed.
_Roff
The index of a character in a string that is the first to be used to initialize character values for the string being constructed.
_Ch
The character value to be copied into the string being constructed.
_First
An input iterator, const_pointer, or const_iterator addressing the first element in the source range to be inserted.
_Last
An input iterator, const_pointer, or const_iterator addressing the position of the one beyond the last element in the source range to be inserted.

Return Value

A reference to the string object that is being constructed by the member functions.

Remarks

The constructors for class basic_string create and initialize strings as follows:

The first and second constructors create a string that is initialized by all or part of a C-string.
The third member function creates a string that is initialized by all or part of an object of type basic_string.
The fourth member function creates a string that is initialized by a specific number of characters of a parameter stipulated value.
The fifth member function creates an empty string.

Example

// basic_string_ctor.cpp
// compile with: /EHsc
#include <string>
#include <iostream>

int main( )
{
   using namespace std;

   // The first member function initializing with a C-string
   const char *cstr1a = "Hello Out There.";
   basic_string <char> str1a ( cstr1a , 5);
   cout << "The string initialized by C-string cstr1a is: "
        << str1a << "." << endl;

   // The second member function initializing with a string
   string  str2a ( "How Do You Do?" );
   basic_string <char> str2b ( str2a , 7 , 7 );
   cout << "The string initialized by part of the string cstr2a is: "
        << str2b << "." << endl;

   // The third member function initializing a string
   // with a number of characters of a specific value
   basic_string <char> str3a ( 5, '9' );
   cout << "The string initialized by five number 9s is: "
        << str3a << endl;

   // The fourth member function creates an empty string
   // and string with a specified allocator
   basic_string <char> str4a;
   string str4b;
   basic_string <char> str4c ( str4b.get_allocator( ) );
   if (str4c.empty ( ) )
      cout << "The string str4c is empty." << endl;
   else
      cout << "The string str4c is not empty." << endl;

   // The fifth member function initializes a string from
   // another range of characters
   string str5a ( "Hello World" );
   basic_string <char> str5b ( str5a.begin ( ) + 5 , str5a.end ( ) );
   cout << "The string initialized by another range is: "
        << str5b << "." << endl;
}

Output

The string initialized by C-string cstr1a is: Hello.
The string initialized by part of the string cstr2a is: You Do?.
The string initialized by five number 9s is: 99999
The string str4c is empty.
The string initialized by another range is:  World.

Requirements

Header: <string>

Namespace: std