Jack - the error message, Not enough input arguments, makes sense since the code is calling the class constructor at the line
obj(m,n) = Pre;
without any input arguments. So when the line
m = size(F,1);
is executed, there is no F and the error appears. Try putting a breakpoint at this line, and then create an instance of this class to verify when this error is being generated.
As for what the line
obj(m,n) = Pre;
is doing, it is just creating an mxn array of objects of the type Pre. This is typical MATLAB code where you want to initialize an array (or matrix) with an object of a data type. For example,
array1(3,5) = uint8(0)
creates a 3x5 array of 8-bit unsigned integers, whereas
array2(12,3) = single(0)
creates a 12x3 array of elements of the single data type.
