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String member function substr
/* String member function substr */
#include <iostream>
using std::cout;
using std::endl;
#include <string>
using std::string;
int main()
{
string s1( "AA1234567890Codings" );
string s2( " AAB" );
string s3;
// test string member function substr
cout << "The substring of s1 starting at location 0 for\n"
<< "14 characters, s1.substr(0, 14), is:\n"
<< s1.substr( 0, 14 ) << "\n\n";
return 0;
}
/*
The substring of s1 starting at location 0 for
14 characters, s1.substr(0, 14), is:
AA1234567890as
*/
The stringstream, ostringstream, and istringstream objects are used for input and output to a string. They behave in a manner similar to fstream, ofstream and ifstream objects. The function str() can be used in two ways. First, it can be used to get a copy of the string that is being manipulated by the current stream string. This is most useful with output strings. The first form (1) returns a string object with a copy of the current contents of the stream. The second form (2) sets s as the contents of the stream, discarding any previous contents. The object preserves its open mode: if this includes ios_base::ate, the writing position is moved to the end of the new sequence. Internally, the function calls the str member of its internal string buffer object.
Generate substring. Returns a newly constructed string object with its value initialized to a copy of a substring of this object. The substring is the portion of the object that starts at character position pos and spans len characters (or until the end of the string, whichever comes first). In C++, std::substr() is a predefined function used for string handling. This function takes two values pos and len as an argument and returns a newly constructed string object with its value initialized to a copy of a sub-string of this object. Copying of string starts from pos and is done till pos+len means [pos, pos+len).
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#include is a way of including a standard or user-defined file in the program and is mostly written at the beginning of any C/C++ program. This directive is read by the preprocessor and orders it to insert the content of a user-defined or system header file into the following program. These files are mainly imported from an outside source into the current program. The process of importing such files that might be system-defined or user-defined is known as File Inclusion. This type of preprocessor directive tells the compiler to include a file in the source code program.
Strings are objects that represent sequences of characters. The standard string class provides support for such objects with an interface similar to that of a standard container of bytes, but adding features specifically designed to operate with strings of single-byte characters. The string class is an instantiation of the basic_string class template that uses char (i.e., bytes) as its character type, with its default char_traits and allocator types. Note that this class handles bytes independently of the encoding used: If used to handle sequences of multi-byte or variable-length characters (such as UTF-8), all members of this class (such as length or size), as well as its iterators, will still operate in terms of bytes (not actual encoded characters).
The cout is a predefined object of ostream class. It is connected with the standard output device, which is usually a display screen. The cout is used in conjunction with stream insertion operator (<<) to display the output on a console. On most program environments, the standard output by default is the screen, and the C++ stream object defined to access it is cout. The "c" in cout refers to "character" and "out" means "output". Hence cout means "character output". The cout object is used along with the insertion operator << in order to display a stream of characters.
To generate random numbers in C++, use the function rand() to generate and print random numbers. So If you want to generate different different random numbers at each time when
