hit enter as an answer

[seanybarra]

ok so i have a do- while loop and I'm trying to format it so when the user types a y or just leaves it blank and hits the enter button it gives a true statement but so far everytime I test by just hitting enter it just keeps newlining. Some help with what to do will be great. thank you guys!

 do 
{
    cout << "hello !!!\n"
         << "would you like another greeting?(y\n)\n";
    cin << response;
    if((toupper(response) == 'Y')||( response == '\n'))
    {
    }
    else
    {
         break;
    }
}while(true);

[i like red pandas]

First of all, it should be cin >> response. The direction of the arrows determine where the data is going.

Second, I believe the >> operator skips whitespace.

[Annatar]

I'm not sure if it works or not, and I can't test it right now, but maybe try using the ASCII table to find the decimal or hexadecimal equivalent of "carriage return" ?

I believe it is the number 13 in decimal.

[MatthewRock]

Use cin.get() function.
I used it some time ago to capture Enter key press("Press enter key to continue"), so you will have no problem using it for your task.

PS. I would recommend you abandoning infinite loop and break statement in favor of bool that would control your loop. Something like this

bool exit = false;
do
{
//Do something
//Get input
//If input is what you wanted( not Y or y in your case) exit = true
}while(exit == false )

[seanybarra]

@ i like red pandas i copied it wrong from my code but it still wont work.

@ mathewrock so would i just use cin.get(response); ?

[seanybarra]

@mathewrock never mind it worked thanks for all your input guys :]

[i like red pandas]

never mind

[MatthewRock]

@i like red pandas - I may be wrong, but...
http://www.cplusplus.com/reference/istream/istream/get/

It looks like it is overloaded to get arguments, and in example code it is used to get C-string. Looks like the thing seanybarra looked for.

[Duthomhas]

When dealing with user input, the correct way is to use std::getline():

string s;
while (toupper( s.c_str[ 0 ] ) != 'N')  // repeat until user enters "N..." or "n..."
{
  cout << randomized_greeting() << endl;
  cout << "again? ";
  getline( cin, s );
}

Hope this helps.

[i like red pandas]

Ah, you're right, disregard me. Though in this case, either method will work.

[MatthewRock]

Duoas is right, preferred way is getline; I just thought of me skipping enter first, and recalled std::get() function, but both methods work. Getline is just more simple and elegant.

[Duthomhas]

@i like red pandas
There was nothing wrong with your answer -- you shouldn't go back and delete stuff.


Dealing with user input is not anywhere near as simple as we tend to think it is (or ought to be).

C++'s stream operators are powerful and tend to lull us into the idea that just getting input and correctly parsing a stream are one and the same. Other languages make it a little less flexible and/or more pedantic.

For example, in Python, to get input you must mystring = raw_input(). Once you have that, you can try to convert it/parse it to whatever you want, which Python makes easy with dynamic typing and built-in string/list processing capabilities.

In C++, you must be a little more explicit about it, and put the sanity checks in all the right spots.


For example, the snippet I posted works because a c-string always has at least one character -- the terminating null. So by checking against the first character in the c-string, there cannot ever be an error on that test -- even if the input stream is in an error state. It is a simple trick for getting a single unconditional character from the user, given the following mantra:

The user will always press ENTER at the end of every input.

Hope this helps.