Swap Problem for Copy in Copy Out using Ada matrices

Routines: Swap Problem Example with ADA Matrices Spring, 2000

The purpose is to provide another example of copy in copy out parameter passing as well as expose the student to some more Ada code.

Since Ada does not specify which parameter passing mechanism to use with arrays this code may or may not work correctly.

With Matrix_stuff; Use Matrix_stuff;
PROCEDURE Swap(x,y: IN OUT matrix) is
BEGIN
x := x + y;
y := x - y;
x := x - y;
END
BEGIN -- Main
   a:=(1..3 => ( 1..3 => 1));
   Swap (a,a);
END;

PACKAGE Matrix_stuff IS
TYPE index is RANGE 1..20;
TYPE matrix is ARRAY(index RANGE <>,
                     index RANGE <>) of INTEGER;
FUNCTION "+" (x,y : IN matrix) RETURN matrix;
FUNCTION "" (x,y : IN matrix) RETURN matrix;
END Matrix_stuff;
PACKAGE BODY Matrix_stuff IS
   FUNCTION "+" (x,y : IN matrix) RETURN matrix IS

L1 : x’FIRST(1);
U1 : x’LAST(1);
L2 : x’FIRST(2);
U2 : x’LAST(2);
z : matrix(L1..U1, L2..U2);

   BEGIN
IF L1 /= y’FIRST(1) or U1 /= y’LAST(1) or
         L2 /= y’FIRST(2)or U2 /= y’LAST(2)
   THEN Raise CONSTRAINT_ERROR;
END IF
FOR i IN L1..U1 LOOP
FOR j IN L2..U2 LOOP
    z(i,j) := x(i, j) + y(i, j);
END LOOP;
END LOOP;
return (z);
END;
FUNCTION ”-" (x,y : IN matrix) RETURN matrix IS

L1 : x’FIRST(1);
U1 : x’LAST(1);
L2 : x’FIRST(2);
U2 : x’LAST(2);
z : matrix(L1..U1, L2..U2);

   BEGIN
IF L1 /= y’FIRST(1) or U1 /= y’LAST(1) or
         L2 /= y’FIRST(2)or U2 /= y’LAST(2)
   THEN Raise CONSTRAINT_ERROR;
END IF
FOR i IN L1..U1 LOOP
FOR j IN L2..U2 LOOP
    z(i,j) := x(i, j) - y(i, j);
END LOOP;
END LOOP;
return (z);
END;
End Matrix_stuff;