What is the difference?

[Gilbert Gosseyn <hnptz@yahoo.de>]

package G is

generic

with function f return Integer is <>;

-- alternativ: with function f return Integer;

procedure gg;

end G;


package body G is

procedure gg is
begin
null;
end gg;

end G;


procedure test is

function f1 return Integer is
begin
null;
end f1;

procedure gg1 is new gg(f => f1);

begin
null;
end test;

It works in both versions.

What is here the meaning of: is <>?