Is it a bad input : cin « Development « C++ Tutorial

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C++ Tutorial » Development » cin

5.1.23.Is it a bad input

#include <iostream>

#include <string>

#include <cmath>



using namespace std;



int main()

{  

   double area;

   cout << "Please enter the area of a square: ";

   cin >> area;



   if (cin.fail())

   {

      cout << "Error: Bad input\n";

      return 1;

   }



   if (area < 0)

   {

      cout << "Error: Negative area.\n";

      return 1;

   }



   cout << "The side length is " << sqrt(area) << "\n";



   return 0;

}

5.1.cin
	5.1.1.	Read int value from keyboard
	5.1.2.	cin Handles Different Data Types
	5.1.3.	Use get() to read a string that contains spaces
	5.1.4.	Use the extraction operator >> with cin.get( ) to process an entire string.
	5.1.5.	cin with strings (cin.getline)
	5.1.6.	cin and atoi, atof functions
	5.1.7.	Using peek() and putback()
	5.1.8.	Concatenate put()
	5.1.9.	Testing error states.
	5.1.10.	Unformatted I/O using cin.read, cin.gcount and cout.write
	5.1.11.	Contrasting input of a string via cin and cin.get
	5.1.12.	Demonstrating member function width
	5.1.13.	Read char array from keyboard, get its length and concatenate two strings
	5.1.14.	Read a character from keyboard
	5.1.15.	Copy all standard input to standard output
	5.1.16.	Manipulator that skips until end-of-line
	5.1.17.	avoids buffer overflow with cin.width
	5.1.18.	Extends std::streambuf to create data buffer
	5.1.19.	Using member functions get, put and eof.
	5.1.20.	Contrasting input of a string with cin and cin.get.
	5.1.21.	Unformatted I/O with read, gcount and write.
	5.1.22.	Character input with member function getline.
	5.1.23.	Is it a bad input

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