Define a new binary operator in MATLAB?

Hi,

I wondered whether it is possible to define a new, binary operator in MATLAB. The thing is, I need a new operator to "multiply" two matrices in an uncommon way, like this:

A = [.5 .5 0; 0 1 0; 0 .5 .5];
B = [.5 .5 0; 0 1 0; 0 .5 .5];

RowsA = size(A,1);
ColsA = size(A,2);

RowsB = size(B,1);
ColsB = size(B,2);

C = zeros(RowsA*RowsB, ColsA*ColsB);

for i = 1:RowsA
    for j = 1:ColsA        
        C( 1+(i-1)*RowsB:i*RowsB, 1+(j-1)*ColsB:j*ColsB ) = A(i,j) * B;        
    end    
end

Instead of making a function and calling C = myfunction(A,B), I'd like to use C = A # B, with # the new operator (or perhaps another symbol if this is not possible).

Answer 1

[Jan]

You cannot define a new operator in Matlab using non-standard symbols like #.

While using myFunction(A, B) is a perfect solution already, you can create a new object type for the matrices and overload the standard operators. E.g. for A+B the code plus(A, B) is called implicitly. But the restriction to standard operator characters +-*/\ and [] will reduce the readability. Therefore I prefer myFunction().

[Pieter]

Thanks @Jan for your answer. Would it perhaps be possible to add some functionality to the ^ operator for matrices? So instead of the A^2 and A.^2 for example, define A^B where A and B are both matrices?

[Walter Roberson]

That would be the method named "mpower", and you would have the same restrictions as Jan noted -- i.e., you would have to use a different object type rather than simple number matrices.