CODEWITHSUNDEEP
c++loopscin
user2795598
user2795598

Reputation: 3

Problems checking for valid cin input

My code: http://pastebin.com/qjFd6KXb

I have an assignment for class that requires me to create a program that will output a simple multiplication question that the user has to answer in three tries or less. One of the requirements is that the program checks that the users guess is a valid number. My professor wants us to use this method in our code:

#include <iostream>
#include <cstdio>
using namespace std;

int main()
{
    char c;
    bool valid = false;
    int i;
    while (!valid)
    {
        cout << "Enter an int " << endl;
        cin >> i;
        valid = true;
        if (cin.peek() != '\n' || cin.fail()) // checks if the input data was correct or not
        {
            valid = false; 
            cin.clear();  // clears the error flags
            cin.ignore(100, '\n'); // ignores up to 100 characters in the cin stream
        }
    }
}

My problem comes in at about line 57 of my code. Without the extra while loop and if statement to check for correctness, it runs fine. However no matter what I try, when I implement that part it either becomes an infinite loop, or impossible to win. If someone could let me know what is wrong with this I'd greatly appreciate it, as I can't for the life of me figure this one out.

Upvotes: 0

Views: 536

Answers (2)

Chemistpp
Chemistpp

Reputation: 2056

Your check can be achieved like this:

    std::cin >> i;
    while( std::cin.fail() ) {
        std::cout << "Bad Input\nEnter an Integer, foo: ";
        std::cin.clear();
        std::cin.ignore('256','\n');
        std::cin >> i;
    }

I'm not sure why you are peaking and looking for the end of line

Upvotes: 0

Stefan Falk
Stefan Falk

Reputation: 25397

Just took a short look at your code.. I think

tries = tries + 1; // Adds one to the tries counter

is in the wrong scope

while ((choice != 1) || (choice != 1) || (choice != 1));   
   cout << "Try to solve the problem!\n"; // Provides instruction to the user.

   while ((result != guess) && (tries < maxtries))
   {
   }  
   tries = tries + 1; // Adds one to the tries counter
}

should be

while (choice != 1);   
   cout << "Try to solve the problem!\n"; // Provides instruction to the user.

   while ((result != guess) && (tries < maxtries))
   {
          tries = tries + 1; // Adds one to the tries counter
   }  
}

Upvotes: 1

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