MATLAB: Does MATLAB call the double constructor on a=a+1

classclassdefMATLABobject-orientedoopoperator overloading

I want to overload the double class and add some properties to it.
And i also have to override the plus function. A similar code could
look like this:
classdef myclass < double
    properties (Access = protected)
        foo
    end
    methods (Access = public)
        function obj = myclass(val,foo)
            obj     = obj@double(val);
            obj.foo = foo;
        end
        
        function out = plus(obj,in)
            out = myclass(plus@double(obj,in),obj.foo);
        end
    end
end
However, if out = in on plus, I could just obj.foo = in.foo and call plus@double(obj,in), could I?
How does MATLAB itself determine, if a plus is in fact an increment, so out = in?

Best Answer

How does MATLAB itself determine, if a plus is in fact an increment, so out = in?
Reference counting.
I do not know about class methods in this regard.
Outside of classes, in-place operations are only done inside a function of the form
function Variable = FunctionName(arguments that include Variable)
and only if the reference count for Variable is 1, and only if the outside output variable name is the same as the input variable name
In-place operations are not even done for simple code like
count = 0;
for K = 1 : 5
    count = count + 1;
end
it would have to be something like
count = 0;
for K = 1 : 5
    count = PlusPlus(count);
end
function var = PlusPlus(var)
  var = var + 1;
end
For more discussion of in-place operations, I recommend searching postings from James Tursa
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