Operator Overloading (int as bool) - c++

Question

I'm trying to write a code that returns 1s and 0s instead of true or false. But this doesn't seem to be right.
int Short_Vector::operator==(const Short_Vector& obj){
if(a == obj.a && b == obj.b && c == obj.c && d == obj.d){
return 1;
}else{
return 0;
}
}
So it should return a value for each variable.
I also tried this:
int Short_Vector::operator==(const Short_Vector& obj){
int a_tf, b_tf, c_tf, d_tf;
if(a == obj.a){
a_tf = 1;
}else{
a_tf = 0;
}
if(b == obj.b){
b_tf = 1;
}else{
b_tf = 0;
}
if(c == obj.c){
c_tf = 1;
}else{
c_tf = 0;
}
if(d == obj.d){
d_tf = 1;
}else{
d_tf = 0;
}
return(a_tf, b_tf, c_tf, d_tf)
}
But I got an error about the commas being an operator.
EDIT
Getting the error: error: conversion from 'int' to non-scalar type 'Short_Vector.
I'm trying to represent a vector that looks like this [9,1,5,5].
Then i'll say
`Short_Vector a(2, 6, 9, 4);
Short_Vector b(3, 8, 7, 6);
Short_Vector c = a == b;
cout<<c;`
Output is then: [0,0,0,0]

Answer 1

The second method can't work because the return type is an 'int' and '(a_tf, b_tf, c_tf, d_tf)' is not an int but 4 ints separated by commas.
Since you want to return 4 booleans you could do the following:
int Short_Vector::operator==(const Short_Vector& obj)
{
//...
return (a_tf) | (b_tf << 1) | (c_tf << 2) | (d_tf << 3);
}
//the caller would do the follwoing:
int result = (MyObject1 == MyObject2);
if(result & (1 << 1) //b_tf is set to 1;
{
}
if(result & (1 << 3) //d_tf is set to 1;
{
}

Answer 2

You can use std::bitset to set a bit for equality of each member
std::bitset<4> Short_Vector::operator==(const Short_Vector& obj){
std::bitset<4> r;
r[0] = (a == obj.a);
r[1] = (b == obj.b);
r[2] = (c == obj.c);
r[3] = (d == obj.d);
return r;
}
And you can use it like
Short_Vector a(1,2,3,4);
Short_Vector b(1,0,3,4);
std::bitset<4> res = (a==b);
std::cout << res;
Should give you
1011
std::bitset is good because it provides convenient methods like all any and none (and many more). So that you can check aggregate values with ease.

Answer 3

If you want to have the result as a Short_Vector, try this:
Short_Vector Short_Vector::operator==(const Short_Vector& obj) {
return Short_Vector(
a == obj.a,
b == obj.b,
c == obj.c,
d == obj.d
);
}

Answer 4

The comma operator won't work the way you presumed. It will actually evaluate each of its operands and return the last. The compiler gave you a warning about this little misconception.
One alternative is to set each bit containing the numeric true/false equivalent of your boolean expressions:
unsigned int n = 0;
n |= (a == obj.a) << 0;
n |= (b == obj.b) << 1;
n |= (c == obj.c) << 2;
n |= (d == obj.d) << 3;
return n;
You can use a smaller datatype like char or you can use std::bitset.

Answer 5

If you must use an int as a return type, you could use the left shift operator and do something like:
int result = 0;
result += a_tf << 3; //Shifts the bit 3 places to the left.
result += b_tf << 2; //Shifts the bit 2 places to the left.
result += c_tf << 1; //Shifts the bit 1 place to the left.
result += d_tf; //Puts d_tf as bit 0
return result;
And to get each one back out use the bit-wise and:
result = obj1 == obj2; //Where obj1 and 2 are your compared objects
int a_tf = (result >> 3) & 1;
int b_tf = (result >> 2) & 1;
int c_tf = (result >> 1) & 1;
int d_tf = result & 1;
Though I have to say Named's solution using a bitset is more easily understood, and inserting/retrieving a single value is much easier that way.