Overloading Equality Operator for Arrays

I have a class with the eq() operator overloaded, but I'm not sure the best way to make it work with object arrays, in a similar way to the way standard arrays work for equality. Here's the code that I have right now. For reference, the class is designed to work with spheres in 3D space, with a center [x, y, z] and a radius.

        function test=eq(a,b)
            if all(size(a.xyz)==size(b.xyz))
                if (a.radius==b.radius)
                    test=all(a.xyz==b.xyz);
                else
                    test=false;
                end
            else
                test=false;
            end
        end

Answer 1

[Matt J]

Perhaps as follows

       function test=eq(a,b)

            test =  all([a.xyz]==[b.xyz]) & all([a.radius]==[b.radius]);

        end

[Daniel Shub]

The ISEQUAL function might be better since it handles unequal size and unequal class vectors.

[Daniel]

A couple of problems with this, since xyz is a 1x3 array, if the object is empty, xyz is just [] and this will through a "matrix dimensions must agree" error, which is why I had the size comparison to start with.

Also, because xyz is a [1x3] double, and I want all of x y and z to be equal, it's necessary to use all( ) on the xyz portion. This works on single objects, but when I do a comparison of arrays, for example a 1x2, if both elements are the same I get [1, 1] as expected, but if one is the same and one is different, I get [0, 0].

[Matt J]

if both elements are the same I get [1, 1] as expected

That expectation was not evident. For all we can tell, you are looking for behavior similar to ISEQUAL, which always returns a scalar true/false output, regardless of the inputs' sizes. You also shouldn't be getting a non-scalar output from my code.

But if you do want non-scalar true/false output, you would instead do this

       function test=eq(a,b)

            if ~isequal(size(a), size(b))
                  error 'Dimension Mismatch'
            end

            xyz_eq=all(vertcat(a.xyz) == vertcat(b.xyz),2); 
                               %assumes xyz are row vectors

            radius_eq=vertcat(a.radius)==vertcat(b.radius);

            test =  reshape(xyz_eq & radius_eq, size(a));
        end

if the object is empty, xyz is just [] and this will through a "matrix dimensions must agree" error, which is why I had the size comparison to start with.

The "dimensions must agree" error is consistent with the normal behavior of EQ for numerical arrays, e.g.,

      >> [1,2,3]==[]
      Error using  == 
      Matrix dimensions must agree.

It's not clear why you would want to be getting rid of it now.