Basic Istream Unget In C++

The basic_istream::unget function is used to unget the character, which also decreases the location by a single character and allows the retrieved character to be reused. The appropriate header file should be provided.

The objective of using the basic_istream::unget method is to return a character to the stream, allowing it to be easily processed at a later stage. This function can lower the location by one character, essentially restoring the previously removed character.

Header File

It included the <iostream> header file.

Syntax:

It has the following syntax:

basic_istream& unget();

Parameters: The basic_istream::unget function takes no parameters.

Return value: The basicistream object is returned by the method basicistream::unget.

The following programs explain std::basic_istream::unget:

Example:

Filename: Ungetting1.cpp

// Program to implement the use of basic_istream::unget() 

#include <bits/stdc++.h> 

using namespace std; 

// main

int main() 

{ 

	// decreasing the size of the string stream

	istringstream con("ProgrammingLanguage"); 

	char a = con.get(); 

	if (con.unget()) { 

		char be = con.get(); 

		cout << "We got: " << a << endl; 

		cout << "After the ungetting, the character is: "

			<< be << endl; 

	} 

	return 0; 

}

Output:

We got: P

After the ungetting, the character is: P

Example 2:

Filename: Ungetting2.cpp

// Program to implement the use of basic_istream::unget() 

#include <bits/stdc++.h> 

using namespace std; 

// main

int main() 

{ 

	// decreasing the size of the string stream

	istringstream con("Language"); 

	char a = con.get(); 

	if (con.unget()) { 

		char be = con.get(); 

		cout << "We got: " << a << endl; 

		cout << "After the ungetting, the character is: "

			<< be << endl; 

	} 

	return 0; 

}

Output:

We got: L

After the ungetting, the character is: L

Explanation:

• ✅ istringstream con("Language");: It initializes an input string stream con using the string "Language".
• ✅ char a= con.get;: If (con. unget) is true, it reads the first letter from the stream ('L') and puts it in variable a. { ... }: Moves to "unget" the character from the stream. The unget method returns the stream location of one character. If successful, it provides true.

Within the if block:

• ✅ char be = con.get;: After unget, reads an element from the stream. It should return the same element that was previously read ('L') because it was "unget" back to the stream.
• ✅ The values of a and be are printed on the terminal.