Incomprehensible Infinite Loop

As far as I understand it, the operator >> is capable of accepting integer arguments when used with the cin stream.

The problem is, when I go crazy on the keyboard and type in a group of numerical characters which far exceeds the size of an integer (on an intel based computer with VC++ 2003) such as 1872634817236491872364817, the value that gets passed to my integer is always (and I mean always) 3435973836.

That is certainly a head scratcher but I have this stream nested inside a while loop and once it receives my crazy input, it never stops at cin and continues going round and round and always passes 3435973836 to my integer.

Here's my code:

Code:

---

while(true)
{
        cin >> input; // input is an integer. Feel free to type in
                        //any very large number at the prompt. Just make
                        //sure it exceeds 2^32. Preferrably much larger.
        s = factorialize(input); // s was declared as a string elsewhere.
        cout << s.c_str() << endl;
}

---

On the off chance that my function "factorialize" is causing the damage, here's the relevant function:

Code:

---

string factorialize(unsigned int input)
{
        bool not_end = false;
        unsigned int max = static_cast<int>(sqrt(static_cast<double>(input)));
        string s;
        for(unsigned int i = 2; i <= max; i++)
        {
                if(input % i == 0)
                {
                        char buf[10];
                        itoa(i, buf, 10);
                        s += buf;
                        s += "x";
                        s += factorialize(input/i);
                        not_end = true;
                        break;
                }
        }
        if(!not_end)
        {
                char buf[10];
                itoa(input, buf, 10);
                s = buf;
        }
    return s;
}

---

What in the world is going on here?

As always, I humbly await your responses.

Don't worry its not your function it is cin
I thought there was a way to validate if what the user inputed was a valid integer datatype and if it wasn't you could just prompt again, but I can't remember.

I dunno. Maybe try flushing cin down the toilet. [This isn't the technical definition of whats really going on, but by golly it should be!]

Code:

---

cin.clear();

---

Code:

---

while(true)
{
        cin >> input;
cin.clear(); // Give that sucker a nice swirly right here. Note last valid INPUT will be processes TWICE as the junk INPUT.. say 12397329478729348782 will be gone.
        count = 0;
        s = factorialize(input);
        cout << s.c_str() << endl;

}

---

The result of reading an integer is implementation defined if the actual input corresponds to a larger value than the integer can store, and a stream will typically be in an error state afterwards. Which (roughly) means the result is compiler and library specific.

cin >> var; has all the same problems that scanf() has in C
- No overflow detection
- Poor error recovery
- leaves unused characters (eg newlines) to foul up other input methods.

If you really want to be sure of what you're getting, you have to read all user input as a string, and then validate it yourself.

Thanks guys. I guess it should have been obvious all along.