Code repetition

[david16]

hello there . I had a little problem with my code which I could solve I suppose to read something from user then tell him if palindrome or not the problem is that any word I enter is palidrome and when I repeat it I also got something wrong Do I have to use array instead?

  #include < iostream >
#include <string>
#include <algorithm>
using namespace std;


bool is_palindrome( string &s)
{
  return  equal ( s.begin(), s.end(), s.rbegin() );
}


int main ()
{
	string input; char choice; int lc = 1;
	
 do {	

	  cout << "\nExecution number " << lc << ":" <<endl;
	  cout << "-------------------" << endl;
     
	  cout << "\nPlease enter a word or a phase :\n" << endl;
      
	  getline ( cin , input );

	  
		is_palindrome ( input );

	 if ( is_palindrome )

		cout << "\n\"" << input << "\"" << " is palidrome.\n" << endl;

	else
		cout << "\n\"" << input << "\"" << " is not palidrome.\n" << endl;

	do {

	   cout << "\nDo you want to do another computation ? Y/N \n" << endl;
	   cin >> choice;
	 
	}while (  choice != 'Y' && choice != 'y' && choice != 'n' && choice != 'N' && cout << "\nSorry wrong input!\n" );
     
	 ++lc;
 
   }while ( choice == 'y' || choice == 'Y' );
	
    cout << "\n";
    system ( "pause" );
	return 0;
}

I tried cin.ignore ( 1000 , '\n' ) before the function call didnt work ;


this is the output I had

Execution number 1:
-------------------

Please enter a word or a phase :

elsa

"elsa" is palidrome.


Do you want to do another computation ? Y/N

y

Execution number 2:
-------------------

Please enter a word or a phase :


"" is palidrome.


Do you want to do another computation ? Y/N

thx for your help

[2kaud]

Firstly,

	is_palindrome ( input );

	 if ( is_palindrome )

Don't you mean

	 if ( is_palindrome(input) )

Didn't the compiler report a problem?

I tried cin.ignore ( 1000 , '\n' ) before the function call didnt work

The solution is to use cin.ignore(), but not at the place where you tried it. Before I show the solution, have a good think about what is happening with the input stream.

[david16]

I guess the input stream are linked together that why We use cin.ignore () but you said I used it in wrong place ??

[2kaud]

I guess the input stream are linked together that why We use cin.ignore () but you said I used it in wrong place ??

Yes.

Also

bool is_palindrome( string &s)

would be better defined as

bool is_palindrome(const string &s)

as the contents of string s isn't/shouldn't change.

[david16]

Oh yes you were right . The position of the cin.ignore () should be at the end of the do while loop that repeat the program . So before the while I plug it there right ??

[david16]

Sorry can you explain why bool is_palindrome(const string &s) with const ?? did know why its better ?

[2kaud]

Oh yes you were right . The position of the cin.ignore () should be at the end of the do while loop that repeat the program . So before the while I plug it there right ??

If you put it there, it may seem to work - but try entering aaa as the input to the 'another computation' prompt.

[david16]

yes but even with bool is_palindrome(const string &s) I'm getting that issue you said . about

[2kaud]

Sorry can you explain why bool is_palindrome(const string &s) with const ?? did know why its better ?

bool is_palindrome(const string &s)

You are passing s by reference, so any changes to s in the function are passed back to the corresponding argument variable in the calling function. If the function is not supposed/required to change s, then passing by const reference will cause a compiler error if s is changed by mistake in the function. Any error detected by the compiler is much better than trying to debug a problem! In general, if the contents of any variable isn't supposed to change, then it should be defined as const.

[david16]

Oh I see what you mean with cin.ignore () . Where you thing I should put it ?

[2kaud]

yes but even with bool is_palindrome(const string &s) I'm getting that issue you said . about

For your code, having const/not const there will make no run-time difference. It's just good practice you should get into the habit of using where appropriate.

Hint. Try moving the cin.ignore() into the other loop.

[david16]

Yes got it . I should put that after the cin >> choice in the first do while loop where I ask if user want to repeat and I receive his choice

[2kaud]

Yes got it . I should put that after the cin >> choice in the first do while loop where I ask if user want to repeat and I receive his choice

yep!

PS Take a bonus point for using equal() to test for a palindrome.

[david16]

thx a lot