MATLAB: Mtimes and transpose are being treated as a single function when used together

MATLABmtimesooptranspose

I'm trying to overload the mtimes function so each * operator will perform my own matrix multiplication (using mex) instead of matlab's built-in function.
I managed to overload the mtimes function when writing it in the same m-file with the calling function, and when I perform A*B I see that my function is being called (using debug message running from my mtimes function). So far so good. But when I perform A*B.' my mtimes is NOT called!. Neither when I perform A.'*B or A.'*B.'.
See the example code below, and the debug messages I see in Matlab console when I run it.
function testme
A = randn(3,3);
B = randn(3,3);
disp('start');
C1 = A*B;
C2 = A*B.';
C3 = A.'*B;
C4 = A.'*B.';
disp('end');
end
function out = mtimes(a,b)
out = a + b; % here should come my mex function. using '+' to let others copy-paste and check it for themselves without the mex being missing.
disp('been in my-mtimes');
end
output on console:
>> testme
start
been in my-mtimes
end
It looks like A*B.' is calling different functions than 'mtimes' following 'transpose'… Any idea which function is called on A*B.' or A.'*B? BTW wrapping B.' in brackets (B.') doesn't change the behavior. Neither using A*transpose(B)… None of them are entering my mtimes function… I guess this is some kind of optimization that matlab does to save the transpose MIPS, but there must be a function that does that, which I can't find… Any help would be appreciated!
Thanks, Koby

Best Answer

To circumvent this, my recommendation would be to overload mtimes in a subclass of type double.
classdef myclass < double                   
        methods
          function obj=myclass(data)      
              obj=obj@double(data);
          end
          function out = mtimes(a,b)
              out = myclass( a + b );
              disp('been in my-mtimes');
          end
        end
end
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