how to copy complete column (or row) of matrix to another?

["Nasser M. Abbasi" <nma@12000.org>]

I have not programmed in Ada for long time. I forgot now if
Ada supports copying whole column or whole row of 2D matrix
in one operation or not?

Here is a toy example. I want to copy one matrix
to another using a loop (to see if this is allowed)

--------------------------
procedure t1 is
    type Matrix is array (Integer range <>, Integer range <>) of Integer;
    A : Matrix  :=
            (( 1,  2,  3),
            (  4,  5,  6),
            (  7,  8,  9));
    B: Matrix(1..3,1..3);
begin -- copy A to B one row at a time

    FOR I in A'range(1) LOOP
        B(I,1..3):=A(I,1..3); -- error at this line
    END LOOP;

end t1;
---------------------

I see old thread that slicing is not allowed for matrix?

https://groups.google.com/forum/#!topic/comp.lang.ada/vwPXMabvUR8
"Copying rows in a two dimensional array."

Is this the reason for the error I get or Am I doing something
silly in the above?

Using gnat 2017

thanks
--Nasser