\Calculate forward differences

\Sets elements of B to the first order forward differences of A.
\A should have bounds 1 :: N, B should have bounds 1 :: N - 1.
procedure FirstOrderFDifference ( A, B, N );
integer A, B, N, I;
for I := 2 to N do B( I - 1 ) := A( I ) - A( I - 1 );

integer V   ( 1 + 10 );
integer Diff( 1 +  9 );
integer VPos, Length, List, I, Order;
begin
    \construct the initial values array
    VPos := 1;
    List:= [90, 47, 58, 29, 22, 32, 55, 5, 55, 73];
    for I := 0 to 10-1 do begin
        V( VPos ) := List( I );
        VPos := VPos + 1
    end;

    \calculate and show the differences
    Format(8, 0);       \set output format
    Length := 10;
    for Order := 1 to Length - 1 do begin
        FirstOrderFDifference( V, Diff, Length );
        Length := Length - 1;
        IntOut(0, Order);  Text(0, " : ");
        for I := 1 to Length do RlOut(0, float(Diff( I ) ));
        CrLf(0);
        for I := 1 to Length do V( I ) := Diff( I )
    end
end