Thread: Input check problem with numbers

Which is the most suitable source code? I need a programmer with a large experience on C++ to answer this question.

Code:

#include <string>
#include <iostream>
#include <limits>

int main()    {
    using namespace std;
    const int THISYEAR = 2007;
    string yourName;
    int birthYear,bad_input;
    
    cout << "What's your name ? " << flush;
    getline(cin, yourName);

   
    do {
      
        bad_input=0;
        cout <<"\nWhat year were you born :" << flush ;
        cin >> birthYear;
        if(!cin.good())   
        {
          
            bad_input=1;
            cin.clear();   
           
       
            cin.ignore(numeric_limits<streamsize>::max(),'\n');
            cout << "This is not valid value" << endl;
        }
    }while(bad_input);
       
    cout << "Your name is " << yourName
         << " and you are approximately "
         << (THISYEAR-birthYear)
         << " years old. " << endl;
   
    return 0;
}

2nd:

Code:

#include <string>
#include <iostream>
#include <limits>

int main()	{
	using namespace std;
	const int THISYEAR = 2007;
	string yourName;
	int birthYear;
	
	cout << "What's your name ? " << flush;
	getline(cin, yourName);
			
	cout <<"What year were you born? " << flush;
	while(!(cin>>birthYear))	
	{
		cin.clear();	
		cin.ignore(numeric_limits<streamsize>::max(),'\n');
				
		cout << "No valid value. ";
		cout <<"What year were you born? " << flush;
	}
			
	cout << "Your name is " << yourName
		 << " and you are approximately "
		 << (THISYEAR-birthYear)
		 << " years old. " << endl;
	
	return 0;
}

3rd

Code:

#include <string>
#include <iostream>
#include <cstdlib>

int main()    {
    using namespace std;
    const int THISYEAR = 2007;
    string yourName;
    int birthYear;
    char temp[100];
   
    cout << "What's your name ? " << flush;
    getline(cin, yourName);
   
    do    {
        cout <<"What year were you born? " << flush;
        cin.getline(temp,100);   
             
        birthYear=atoi(temp);
        if (birthYear==0)    {
            cout << "Invalid valude..." << flush;
        }
    } while(birthYear==0);
   
   

       
    cout << "Your name is " << yourName
         << " and you are approximately "
         << (THISYEAR-birthYear)
         << " years old. " << endl;
   
    return 0;
}

5th

Code:

#include <string>
#include <iostream>
#include <sstream>       // for istringstream convert()
using namespace std;

int main()
{
    const int THISYEAR = 2007;
    string yourName;
    int birthYear;
    string birth;               //για το έτος γέννησης
   
    cout << "What's your name ? " << flush;
    getline(cin,yourName);
    for(;1;)    {
             cout << "What year were you born? ";
             getline(cin,birth);
             // μετατροπή string -----> int
             istringstream convert(birth);
             // τοποθέτηση στην int birthYear
             convert >> birthYear;
                 // αν δεν πετύχει σημαίνει ότι δεν είναι αριθμός
                 if(!convert    {
                    cout << " This is not valid.Try again...." << endl;
                     continue;
                } else {
                    break;
                }
    }
   
    cout << "Your name is " << yourName
             << " and you are approximately "
             << (THISYEAR-birthYear)
             << " years old. " << endl;
   
  
   
    return 0;
}

6th

Code:

    #include <string>
    #include <iostream>
    #include <cstdlib>        //Για να κάνεις calls σε commands από το prompt π.χ. την PAUSE, επίσης έχει την atoi
    #pragma argsused

    //Ελέγχει εαν το string περιέχει αριθμό
    // εαν ναι επιστρέφει true
    // αλλιώς επιστρέφει false
    bool CheckStr(const std::string& s)
    {
       for (int i = 0; i < s.length(); i++) {
           if (!std::isdigit(s[i]))
    		   return false;
       }
       return true;
    }

    //Παίρνει το όνομα
    void GetName(std::string& yourName)
    {
    	using namespace std;
    	cout << "What's your name ? " << flush;
    	getline(cin, yourName);
    }

    //Παίρνει την ημ. γέννησης
    void GetBirthdate(std::string& birthYear)
    {
    	using namespace std;
    	cout << "What year were you born? ";
    	getline(cin, birthYear);
    }

    int main(int argc, char* argv[])
    {
    	using namespace std;
    	const int THISYEAR = 2007;
    	string yourName;
    	string birthYear;
    	int intYear;
    	bool exit = false;

    	//Μέχρι να δώσει σωστή ημ. ο χρήστης το πρόγραμμα κάνει loop
    	while (!exit)
    	{
    		GetName(yourName);			//Παίρνει το όνομα
    		GetBirthdate(birthYear);	//Παίρνει την ημ. γέννησης


    		if ( CheckStr(birthYear) ) { 	//Εάν η ημερομηνία είναι σωστή
    			  intYear = atoi(birthYear.c_str() ); 	//Μετατρέπει το string σε integer
    			  cout << "Your name is " << yourName
    				<< " and you are approximately "
    				<< (THISYEAR-intYear)
    				<< " years old. " << endl;
    				exit = true;
    		}
    		else {
    			  cerr << "This is not valid."
    				<< " Try again..." << endl;
    		}
    	}

    	system("PAUSE");
    	return 0;
    }

Thanx for your time

Ok guys here it is the deal.

I want to make a program that prints out your age. It asks for your name and for your date of birth. The BIG problem is that I want to check the birth variable. If you type 1989 then it's ok. But what if you type a character such as a instead of a number ?

I found that there are two solutions.
1)The first one is using direct input and checking the values like this way:

Code:

cout <<"What year were you born? " << flush;
	while(!(cin>>birthYear))	//if the input stream has problems
	{
		cin.clear();	// cancel the fail state of the input sream
		cin.ignore(numeric_limits<streamsize>::max(),'\n');  // thrash the garbage chars
				
		cout << "No valid value. ";
		cout <<"What year were you born? " << flush;
	}

or the
2) second solution is using a convertion of string to an integer using atoi() or istringstream convert().

Which method is better ?


PS: Sorry for the comments...it's Greek Language due to by cources.
Thank you for your time!!!!!

In general, both methods work the same and just as well.
For which is more efficient, I can't say, but I don't believe there's a difference. My preffered method is the second solution.

If you choose the second method, then you have to create one extra string variable which means more RAM is needed.

Just check out this:

Code:

#include <string>
#include <iostream>
#include <limits>

#define THISYEAR 2007


int main()	{

	using namespace std;
	string yourName;
	int birthYear;
	
	cout << "What's your name ? " << flush;
	cin >> yourName;
	
	cout << "What year were you born? ";
	cin >> birthYear;

	while(!cin.good() || birthYear <= 0 || birthYear >= THISYEAR)	{
		cin.clear( );
		cin.ignore( numeric_limits<streamsize>::max( ), '\n');
		cout << "No Valid value. What year were you born? " << flush;
		cin >> birthYear;
	  }


		
	cout << "Your name is " << yourName
		 << " and you are approximately "
		 << (THISYEAR-birthYear)
		 << " years old. " << endl;
	
	return 0;
}

Is this method ok ? Are you applied with that or there's something that I should fix it ?
Thank You!!!!

I don't understand what you mean...

Don't use flush unless necessary. Output is buffered for a reason.
Your code is also very error prone. If a user enters a string instead of an integer, the rest of the cins will fail.