Thread: Can't figure out what is wrong with this

  1. #1
    Registered User
    Join Date
    Feb 2006

    Can't figure out what is wrong with this

    I am trying to design an algorithm for a simple calculator function. But everytime i enter in a symbol to have it perform an operation it always adds. Also, the while loop never terminates even when i say no.

    #include <iostream>
    using namespace std;
    int main ()
    	// Variable Declarations
    	int num1, num2, num3, num4;
    	char letter, symbol;
        // Prompt 
    	cout << "This Program will add, subtract, multiply, and divide" 
    		 << "the two numbers you enter." << endl;
        cout << endl;
    	while (letter = 'y')
    		cout << "Please enter two numbers: ";
    		cin >> num1 >> num2;
    		cout << endl;
    		cout << "Please input the operation you would like to use: ";
    		cin >> symbol;
    		cout << endl;
    		if (symbol = '+')
    			 num3 = num1 + num2;
    		     cout << "The sum is: " << num3 << endl;
            else if (symbol = '-')
    		     num3 = num1 - num2;
    		     cout << "The difference is: " << num3 << endl;
    		else if (symbol = '*')
    		     num3 = num1 * num2;
    		     cout << "The product is: " << num3 << endl;
    		else if (symbol = '/')
    		     num3 = num1 / num2;
    		     num4 = num1 % num2;
    			 cout << "The quiotient is: " << num3 << "The remainder is: " << num4 << endl;
    			cout << "Invalid symbol." << endl;
    		cout << "Would you like to run the program again [y/n] ";
    		cin >> letter;
    		cout << endl;
            cout << "End of Program" << endl;
    	return 0;

  2. #2
    Registered User Tonto's Avatar
    Join Date
    Jun 2005
    New York
    '==' is the comparison operator.
    '=' is the assignment operator.

    Common mistake.

  3. #3
    Registered User
    Join Date
    Nov 2005
    Also, where are you assigning letter to 'y'? (Besides in the while loop, where you obviously don't want to. That is the reason your while loop will not terminate.)

  4. #4
    The Richness... Richie T's Avatar
    Join Date
    Jan 2006
    with regards the previous post and the code you supplied, i am
    assuming that you want to loop over while the user enters 'y'.
    you have:

    while (letter = 'y')
    which as already pointed out, should be changed to:

    while (letter == 'y')
    thats fine, but then when you start your program, what value
    is in the variable y? when you declare a variable, it already has
    some junk value in it (left over from something else). you will
    need to initialise the variable letter as follows:

    char letter = 'y', symbol;
    otherwise, even if you make the changes suggested, the program
    still wont work. just trying to explain something that is easily
    overlooked by beginners
    No No's:
    fflush (stdin); gets (); void main ();

    Example of fgets (); The FAQ, C/C++ Reference

    My Gear:
    OS - Windows XP
    IDE - MS Visual C++ 2008 Express Edition

    ASCII stupid question, get a stupid ANSI

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