comparing strings & dodgy forever loop - help!

Hi all

Hoping someone can help me... I'm a C++ noob and I'm writing a simple "text adventure" (older members will know what that is!!) to help hone my skills (if that's what they can be called at this stage!).

However I'm having two problems with the below member function:

Code:

---

void Office::user_input(door* pDoor, object* pObject, object* pFurniture, Room* pRoom)
{
        string choice;
        bool exit = false;
        for ( ; ; )
        {
        cout << "What would you like to do? ";
        cin >> choice;
       
        if (choice=="open door")
                pDoor[0].open();
        else
                cout << "Not to worry, this is only a test.";
       
        if (exit==true)
                break;
        }
}

---

Firstly, the program is not recognising the link between choice and "open door" if I type in "open door" in the resulting console - it skips and goes straight to the else section. I have tried replacing the type of 'choice' from string to char* and using strcmp - however this didn't make any difference.

Secondly, for some reason after typing in your command it is looping twice, ie printing "not to worry, this is only a test" and "what would you like to do?" twice before pausing to let the user type in their command again.

I don't know if the two problems are related (although it seems doubtful). If anyone could shed any light it'd be really helpful. Cheers!

J

I've no idea why, but putting:

Code:

---

getline(cin, choice);

---

instead of

Code:

---

cin >> choice;

---

seems to work.

Perhaps a more experienced programmer could enlighten us as to why. I have a feeling it's something obvious that will embarrass us :P

well well, the two are linked after all. Nice work Mr Pointer!

But I'm in total agreement... can anyone explain the why please?!! :-)

>> only reads until whitespace. When you type in "open door", it first reads "open". Then the loop restarts, finds that it still has "door" in the input buffer, gives you that, and doesn't even wait for input. So it takes two iterations to get to the input situation again, and you never get "open door".

getline, on the other hand, reads until a newline, so it catches "open door" the first time around.

Be careful when mixing >> and getline. >> leaves whitespace in the stream, including newlines, whereas getline doesn't. So if you do a >> and follow up with a getline, chances are that the getline will read the newline that was left in the stream and immediately return, without waiting for input.

Makes sense... many thanks!!

doh... I'm now having another problem with this :(

This is the updated code:

Code:

---

        string choice;
        bool exit = false;
        for ( ; ; )
        {
        cout << "What would you like to do? ";
        getline (cin, choice);
       
        if (choice=="examine door" || "examine the door")
                pDoor[0].examine(pObject);
        else if (choice=="open door" || "open the door")
                pDoor[0].open();
        else
                cout << "I don't understand the command you've entered.";
       
        if (exit==true)
                break;
        }

---

It would now appear that regardless of what I type into the resulting console, the first option (to examine the door in this case) is always invoked.

It would be a real shame if I ended up taking a sledgehammer to my laptop, so could anyone intervene before this happens?...

J

You need to compare choice with each of the string literals, e.g., (choice == "examine door" || choice == "examine the door"). At the moment what is happening is that even if choice is not equal to "examine door", "examine the door" will then be evaluated as true, hence the first option will always be selected.