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copied!<p>You really keep moving the goalposts. Your new additions are, in a word, terrible: they don't compile at all and they are a smattering of obviously cut-and-pasted code as evidenced by mismatching function-names (e.g. <code>Int_Is_Valid</code>/<code>Pair_Is_Valid</code>).</p> <p>First, let's use a signature-package.</p> <p><code>signature.ads</code> </p> <pre><code>generic Type Item is private; Default : in Item; package SIGNATURE is end SIGNATURE; </code></pre> <p><code>foo.ads</code></p> <pre><code>with System, SIGNATURE; generic with package Item_Pkg is new SIGNATURE(<>); Addr : System.Address; with function Is_Valid(X : Item_Pkg.Item) return Boolean is <>; package Foo is use Item_Pkg; function Read_Eeprom return Item; function Is_Valid (Data_Ptr : access Item) return Boolean; private Port : Item; pragma Volatile( Port ); Pragma Import( Convention => Ada, Entity => Port ); For Port'Address Use Addr; end Foo; </code></pre> <p><code>foo.adb</code></p> <pre><code>package body Foo is function Read_Eeprom return Item is Result : constant Item:= Port; begin if Is_Valid(Result) then return Result; else return Default; end if; end Read_Eeprom; function Is_Valid (Data_Ptr : access Item) return Boolean is begin return Is_Valid(Data_Ptr.all); end Is_Valid; end Foo; </code></pre> <p><code>driver.ads</code></p> <pre><code>package Driver is MAX_INT : constant Integer := 100; MIN_INT : constant Integer := 0; -- Special / Non-Scaler Type type Pair_Type is record X : Integer; Y : Integer; end record; -- Is Valid **USING OVERLOADS** function Is_Valid(Int : Integer ) return Boolean; function Is_Valid(Pair : Pair_Type) return Boolean; My_Int : Integer; My_Pair : Pair_Type; private Default_Pair : constant Pair_Type := (0,0); Default_Integer : constant Integer := 0; end Driver; </code></pre> <p><code>driver.adb</code></p> <pre><code>with Foo, SIGNATURE; package body Driver is -- Is Valid function Is_Valid(Int : Integer) return Boolean is (Int <= MAX_INT and Int >= MIN_INT); function Is_Valid(Pair : Pair_Type) return Boolean is (Pair.X'Valid and Pair.Y'Valid); package Int_pkg is new SIGNATURE(Integer, 0); package Pair_Pkg is new SIGNATURE(Pair_Type, Default_Pair); -- Using defaults for Is_Valid. package Int_Obj is new Foo (Item_Pkg => Int_Pkg, Addr => My_Int'Address ); package Pair_Obj is new Foo(Item_Pkg => Pair_Pkg, Addr => My_Pair'Address ); end Driver; </code></pre> <hr> <p>Given the rather obvious structuring of your code around <code>access</code>-types, I'm guessing that you are trying to "import" knowledge from C or C++. That's going to cause you a lot of trouble/work later on if you try using Ada like it's a C-style language.</p> <p>Also, it may be beneficial to sit down, take a breath, and think about things <a href="http://blog.kickin-the-darkness.com/2007/08/fundamental-theory-of-ada.html" rel="nofollow">in terms of types</a> both the problem-space and, separately, the architecture.</p>

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