The Contents of Limited Types Passed as "in" Parameters
can be modified using the following technique:
with Ada.Text_IO; use Ada.Text_IO;
procedure Rosen_Trick is
type T;
type Relay_Type (Reference : access T) is limited null record;
type T is limited
record
Relay : Relay_Type (T'Access);
Data : Natural := 0;
end record;
function Next (X : in T) return Integer is
Data : Natural renames X.Relay.Reference.Data;
begin
Data := Data+1;
return Data;
end Next;
Test_T : T;
begin
for N in 1 .. 10 loop
Put_Line(Integer'Image(Next(Test_T)));
end loop;
end Rosen_Trick;
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