logical comparison operator - c++

Question

Here is my code for my logical comparison operator (==) overloaded. I use this to check if two strings are identical in size and content. It should return false otherwise.
bool MyString::operator==(const MyString& other)const
{
if(other.Size == this->Size)
{
for(int i = 0; i < this->Size+1; i++)
{
if(&other == this)
return true;
}
}
else
return false;
}
When I ran valgrind it told me warning control reaches end of non-void function. Any suggestions on how to fix this issue and what I could do to better the code?

Answer 1

When control reaches the end of your for loop, you immediately get to the end of the function without returning a value.
It looks to me like you have the logic in your for loop munged anyway -- it's comparing the address of the other item to this. While it's sort of okay to do that, you only need to do it once, not in a loop.
In the loop, you undoubtedly want to compare the characters in the string, not the addresses of the objects.
Edit:
A typical implementation would be something on this general order:
class MyString {
char *data;
size_t length;
public:
// ...
bool operator==(MyString const &other) const {
if (length != other.length)
return false;
for (int i=0; i<length; i++)
if (data[i] != other.data[i]) // If we see any inequality
return false; // they're not equal
return true; // all equal, so the strings are equal.
}
};

Answer 2

It's not too clear what determines equality if the sizes are equal, but
the loop suggests that you're looking for something like:
bool
MyString::operator==( MyString const& other ) const
{
return size == other.size && std::equals( ??? );
}

Answer 3

Well, first of all, if you enter the for loop, and the condition &other == this will not be met, you will never return anything. To fix this, you should just remove the else statement. This will cause your function to return false either if the other.Size == this->Size condition is not met, or if you've gone through the whole loop, and have not used return inside of it.
The second problem is the line if(&other == this). I believe that inside of the loop you intend to check all the symbols of the strings. But now you are only checking the pointer to the class itself. To check the characters, you will need to use something like if( other->data == this->data ), provided you have a data member in which you store the...data (sorry for tautology).
Another little flow is in the design. You see, to check that the strings are equal, you need to look through each and every character and check that they match. However, to prove the strings are not equal, you need to find just 1 pair of characters that does not match. After that, it is pointless to continue comparing. So it is better to changee your condition in the cycle to a negative one, in order to stop comparing immediately after you fuond a pair that does not match, and not to do useless comparations of other characters.
Generaly, it is a good practice to return all the errors as fast as it's possible and avoid unneeded cumputation. So if you can check something in the begining of your function with a simple check, better do it.
So, after all, you should have something like this:
bool MyString::operator==(const MyString& other)const
{
if(other.Size != this->Size)
return false;//If the sizes do not match, no need to check anything else. Just return false.
//If we are here, the sizes match. Lets check the characters.
for(int i = 0; i < this->Size+1; i++)
{
//If some pair doesnt match, the strings are not equal, and we exit.
if( other->data[i] != this->data[i])
return false;
}
//If we are here, all the characters did match, so we return true.
return true;
}

Answer 4

Just get rid of the else. This way there is a "default" behaviour returning false if the condition is not met. It's the functionality you intend, and the compiler or syntax checker won't complain.