Pset3 Music - "unused parameter" and "reaching end of non-void function"

Question

I've been working on my music code for quite some time now, and keep running into the same issue. Whenever I try to compile my code, I get "unused parameter" and "control reaches end of non-void function" errors. From my online searches, these errors have to do with the function possible not returning anything at all, while it's been declared as a non-void function. I haven't been able to see this in my code though, as I thought I covered all possible scenario's.

I tried using Help50, but this didn't give me much more information ("Ensure that you function will always return a value")

Any help would be greatly appreciated! FYI, this is just my is_rest and duration code, as I wanted to fully understand these parts first before diving into frequency.

int duration(string fraction)
{
    // Variable f for converting third element of fraction
    int result;
    int f;
    f = atoi (fraction[2]);

    // If numerator is 1, assign results for subsequently denominators 8/4/2/1
    for (fraction[0] == 1)
    {
        if (f == 8)
        {
            result = 1;
        }
        else if (f == 4)
        {
            result = 2;
        }
        else if (f == 2)
        {
            result = 4;
        }
        else if (f == 1)
        {
            result = 8;
        }
    }

    // Check for numerator = 3 and denominator = 4
    for (fraction[0] == 3)
    {
        if (f == 4)
        {
            result = 6;
        }
        else
        {
            return 0;
        }
    }

    // Output result
    return result;
}

// Determines whether a string represents a rest 
bool is_rest(string s)
{
    if (s[0] == '"')
    {
        return true;
    }
    else if (s[0] != '"')
    {
        return false;
    }
}

----- EDIT: new code per 2/27/2018 ------

// Converts a fraction formatted as X/Y to eights
int duration(string fraction)
{
    // Variable f for converting third element of fraction into integer
    int result;
    int f;
    f = atoi (fraction[2]);

    // If numerator is 1, assign results for subsequently denominators 8/4/2/1
    if (fraction[0] == 1)
    {
        if (f == 8)
        {
            result = 1;
        }
        else if (f == 4)
        {
            result = 2;
        }
        else if (f == 2)
        {
            result = 4;
        }
        else if (f == 1)
        {
            result = 8;
        }
        else
        {
            return 1;
        }
    }
    // Check for numerator = 3 and denominator = 4
    else if (fraction[0] == 3)
    {
        if (f == 4)
        {
            result = 6;
        }
        else
        {
            return 1;
        }
    }
    else
    {
        return 1;
    }

    // Output result
    return result;
}


// Determines whether a string represents a rest
bool is_rest(string s)
{
    if (s[0] == '"')
    {
        return true;
    }
    else if (s[0] != '"')
    {
        return false;
    }
    return true;
}

Answer 1

 for (fraction[0] == 1)

This is an incorrect use of a loop, I think it worthwhile to read thoroughly about the for loops, you have a boolean value within a for loop that is effectively not used. Maybe you wanted an IF comparison?

As for your function is_rest does not return any value even if you do not believe it, the return statement must not be in a conditional block as you do, because at compile time the compiler has no way of "knowing" what value is going to return, the solution would be to put a return statement by default at the end of the function:

bool is_rest(string s)
{
    if (s[0] == '"')
    {
        return true;
    }
    else if (s[0] != '"')
    {
        return false;
    }
    return false; // or true
}