Why am I getting warnings that function "doesn't always return a value" ?

This is a discussion on Why am I getting warnings that function "doesn't always return a value" ? within the C++ Programming forums, part of the General Programming Boards category; I have been working on this program that is a timed mathematical quiz and have everything completed. The problem is ...

  1. #1
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    Question Why am I getting warnings that function "doesn't always return a value" ?

    I have been working on this program that is a timed mathematical quiz and have everything completed. The problem is I keep getting warnings when I compile that says 1: 'sign' : not all control paths return a value and 2: 'equation' : not all control paths return a value. Can anyone help me see what the problem is?

    Code:
     
    #include<iostream>
    
    using std::cout;
    using std::cin;
    using std::endl;
    
    #include<cstdlib>
    
    #include<ctime>
    
    int num();                                // function prototype 
    char sign();                              // function prototype
    int equation( int a, char c, int b );     // function prototype
    
    int main()
    {
    	srand( time( 0 ) );   // This time function returns the current 
    	                      // "calendar time" in seconds.  This value is
    	                      // converted to an unsigned integer and used as 
    	                      // the seed to the random number generator.
    
    	int numcorrect = 0;  
    	int stop = time( 0 ) + 30;
    	int x, y, answer, correctanswer;
    	char z;
    
    	while ( time( 0 ) < stop )
    	{	
    		x = num(), y = num();    // Assignment of x and y to the num function
    		z = sign();
    
    		cout << "What is " << x << " " << z << " " 
    			 << y << endl;       // Prompt to ask the arithmetic question
    		cin >> answer;           // Input answer
    
    		correctanswer = equation( x, z, y ); // Assignment of correctanswer
    		                                     // to the equation function
    
    		if ( correctanswer == answer )       // tests user's answer
    		{
    			cout << "Very good!\n\n"; 
    			++numcorrect;
    		}
    		else
    		{
    			cout << "Incorrect.\n"; 
    			cout << "The correct answer is " << correctanswer << "\n\n";
    		}
    
    	}                                        // end while loop
    
    	cout << "\nYou answered " << numcorrect 
    		 << " questions correctly.\n\n";     // Prompts # of correct answers
    	
    	return 0;
    }
    
    // Function implementation
    int num() 
    {
    	return 1 + ( rand() % 12 );    // returns random integer between 1 and 12
    }
    
    // Function implementation
    char sign()
    {
    	int k = 1 + rand() % 5;   // assigns random integers between 1 and 5 to k
    
    	if ( k == 1 )             // tests k and returns the + sign
    		return '+';
    
    	if ( k == 2 )             // tests k and returns the - sign
    		return '-';
    
    	if ( k == 3 )             // tests k and returns the * sign
    		return '*';
    
    	if ( k == 4 )             // tests k and returns the / sign
    		return '/';
    
    	if ( k == 5 )             // tests k and returns the % sign
    		return '%';
    }                             // ends the sign function implementation block
    
    // Function implementation
    // a, c, and b below are parameters to 
    // the equation function implementation
    int equation ( int a, char c, int b )
    {
    	if ( c == '+' )           // tests c to return the appropriate equation
    		return a + b;
    
    	if ( c == '-' )
    		return a - b;
    
    	if ( c == '*' )
    		return a * b;
    
    	if ( c == '/' )
    		return a / b;
    
    	if ( c == '%' )
    		return a % b;
    }                            // ends equation function implementation block

    Thank you!
    teeCee

  2. #2
    Registered User HaLCy0n's Avatar
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    77
    There are no else's in those functions, so if something doesn't match any of the if statements, it falls off the end of the function without returning anything.

  3. #3
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    Thanks alot!!

    Wouldn't the else statements really be unnecessary though since the way it's set up, there are no possibilities for a false?

    I wanted to use the case structure instead, but I just wasn't able to get it to work.

    Thanks again,
    teeCee

  4. #4
    I lurk
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    1,361
    If you really want to shut the compiler up, just stick a return 0; at the end of both of the functions. In some instances this warning is useful, others, it's just annoying.

  5. #5
    Registered User HaLCy0n's Avatar
    Join Date
    Mar 2003
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    In your situation, its unnecessary. That's why its a warning and not an error. The compiler doesn't exactly know what is going to happen, but it is possible for your function to not return anything, as it sees it.

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