Nested Loop

Nested Loops

Video Summary: https://youtu.be/FHpbU0vyPaU

The body of a loop can contain any type of statement including another loop such as a while loop, a do-while loop, or a for loop. A loop inside another loop is called a nested loop.

The following program counts the number of characters on each line in a file. We know that the I/O manipulator endl forces the next character sent to the output stream to begin a new line. How can we recognize a new line in the input stream? A new line begins following the symbol '\n'. We must be sure to use function .get() defined in iostream, not the extraction operator, to input each character. Otherwise, we will skip all blank spaces including line characters.

// Program LineCt counts the number of characters per line
// and the number of lines in a file.
// Assumption:  There is a '\n' before the EOF.
#include <iostream>
#include <fstream>
using namespace std;

int main()
{
    int lineNo;
    char character;
    int number;
    ifstream inData;  //declares input stream

// bind the input stream name inData to the file "Input.txt"
    inData.open("Input.txt");
    if (!inData)
    {
       cout << "Can't open the input file successfully." << endl;
       return 1;
    }
 
    lineNo = 0;

//Use get function to read data from file "Input.txt"
    inData.get(character);

//while the input stream is not in the fail state
    //e.g. while not EOF, go into the loop
    while (inData)
    {
	lineNo++;
	number = 0;

//while not "end of line", go into the loop
	while (character != '\n')
	{
	    number++;
	    inData.get(character);
	}
	cout << "Line " << lineNo  << " contains "
	     << number  << " characters."  << endl;
	inData.get(character);
    }

inData.close();

return 0;
}

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