做/循环不循环时

Question

I am a beginner in C++ and I was doing a do/while loop exercise and I am having trouble with it recognising the condition let alone it not looping properly. Can you guys give me a good foundation on how a simple problem like this is solved? I want to try and use a string to fulfill the condition of the do/while loop.

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

int main ()
{
    double mean = 0;
    string continuer;
    do
    {
        cout << "Do you want to proceed?" << endl;
        getline (cin, continuer);
        cout << "something" << endl;
        cin >> mean;
    }
    while (continuer == "Y" || continuer == "y");

    return 0;
}

Answer 1

What I gather from your question and comment, you want to iterate through the loop at user's will.

You just want a char variable for that, like this.

string input ;
int number = 0 ;

do
{
  cout << "Please enter a number" << endl ;
  cin >> number ;
  cout << "If you want to continue, Press Y" << endl ;
  cin >> input ;

} while (input == "Y" || input == "y") ;

This do-while loop will execute at least one time, because the condition gets checked at the end of the loop execution. So even if the user does not press Y when asked the first time, this loop would have been executed once. After that, it will go on as long as the condition is fulfilled.

Learn more about the do-while loop here.

http://www.cplusplus.com/doc/tutorial/control/

Answer 2

What do you see? The body of the loop should be executed at least once. Does that happen?

Also, Continuer can be longer than one character, for instance "Y\\n". Do test for that.

Here is what I would do:

#include <string>
#include <sstream>
using namespace std;



    int main ()
    {
        double number = 0;
        string continuer;
        int loop = 0
        do
        {

            cout << "Do you want to proceed?" << endl;
            getline (cin, number);
            cout << "something" << endl;
            cin>> mean;
            getline (cin, continuer);

            cout << "Your answer was '" << continuer << "'." << endl;
            loop = strcmp("Y", continuer);
            if (loop != 0) strcmp("y", continuer);
            if (loop == 0) cout << "Your choice is to stop." << endl;
            else cout << "Your choice is to continue." << endl;
        } while (loop == 0);
        cout << "Bye" << endl;
        return 0;
    }

Be as explicit as you can untill you are confident enough in the language and the algorithm you are working with. It is easier to see what is happening and when it works it is easy to remove the 'cout' lines.