oops? not sure. operator overloading (possible) problem

yeah.... can somebody take a quick look at the unfinished code below and let me know if i'm properly overloading the operators? thanks.

Code:

---

matrix matrix::operator + (matrix other) {
        int y, x;
        this->accesserror = false; other.accesserror = false;
        if ((this->getrows() == other.getrows()) && (this->getcols() == other.getcols())) {
                matrix temp(this->getrows(), this->getcols());
                for (y = 1; y <= this->getrows(); y++) {
                        for (x = 1; x <= this->getcols(); x++) {
                                temp.setelem(y, x, (this->at(y, x) + other.at(y, x)));
                                if ((this->accesserror) || (other.accesserror) || (temp.accesserror)) { break; }
                        }
                        if ((this->accesserror) || (other.accesserror) || (temp.accesserror)) { break; }
                }
        } else {
                matrix temp(1, 1);
                temp.setelem(1, 1, 0);
                this->accesserror = true; other.accesserror = true;
        }
        return temp;
} /*Matrix addition; make sure to check fail() */

---

and

Code:

---

bool matrix::operator == (matrix other) {
        int y, x;
        this->accesserror = false; other.accesserror = false;
        /*Row and column check */
        if (!((this->getrows() == other.getrows()) && (this->getcols() == other.getcols()))) {
                return false;
        }
        else {
                for (y = 1; y <= this->getrows(); y++) {
                        for (x = 1; x <= this->getcols(); x++) {
                                if ((this->at(y, x) != other.at(y, x)) {
                                        return false;
                                }
                        }
                }
        }
}

---

in your op+ you return a variable (temp) that's gone out of scope and will not compile. I'd also consider throwing an exception instead of return a 'null' matrix with an errorbit. Even better would be to use a template for the matrix so adding different sizes won't compile.

Code:

---

matrix<2, 1> m1;
matrix<2, 5> m2;

matrix<> m3 = m1 + m2; /// arrgggh compiler error!

---

'better compile-time then run-time and better run-time then never'

it's pretty easy to add two incompatible matrices and not check accesserror.
it's also pretty tedious to do this each time

Code:

---

matrix m1, m2;
matrix m3 = m1 + m2;
if (m3.accesserror )
{
  // erm, do something useful
}

---

in your op== you need a return true at the end of the method.

well i haven't learned templates (knew only C until last week) but umm... what do u mean out of scope?

That part was wrong. If the copy constructor works properly, there is nothing to worry about here.

A possible efficiency problem lies in your passing the argument by value. You should change it to const reference.

huh?
i don't have a copy constructor......

what part was wrong?

Quote:

---

Originally Posted by CornedBee

That part was wrong. If the copy constructor works properly, there is nothing to worry about here.

A possible efficiency problem lies in your passing the argument by value. You should change it to const reference.

---

you're right about the reference, but unless I'm completely stoned (and I don't think I am) he's returning a variable that's already gone out of scope

Code:

---

// edited for clarity
matrix matrix::operator + (matrix other)
{
    if (someCondition)
    {
        matrix temp(this->getrows(), this->getcols());
        // some stuff
    } // temp out of scope here
    else
    {
        matrix temp(1, 1);
        // more stuff
    } // 2nd temp out of scope

    // where'd this come from?
    return temp;
}

---

I am not talking about return a copy of a local temporary (I know how copy ctors work :P ), I'm talking about a syntax error.

?????????????????
so variables go out of scope after conditionals? bleh. i never knew that.... or didn't remember. probably the first

Quote:

---

Originally Posted by w00tw00tkab00t

?????????????????
so variables go out of scope after conditionals? bleh. i never knew that.... or didn't remember. probably the first

---

the {} braces are c/c++'s scope delimiters. anything created within a matching set of {}'s is automatically cleaned up at the end of that set. (in C, local stack variables used to be called auto-vars).

so,

Code:

---

void func()
{
    int outer = 0;
    {
        int inner = 0;
    }// inner dies here
 
    inner = 2; // compile error!!

    if (outer)
    {
          int ifVar = 0;
    } // ifVar dies here

    ifVar = 2; // compile error!!

    while(true)
    {
          int loopVar = 0;
    } // guess what happens to loopVar here?

    loopVar = 2; // compile error!!

} // outer dies here

outer = 2; // compile error!!

---

Quote:

---

Originally Posted by w00tw00tkab00t

?????????????????
so variables go out of scope after conditionals? bleh. i never knew that.... or didn't remember. probably the first

---

Sorry, you're right. Didn't read the function closely enough.