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POAda: tagged type---inheritance from parent package
 

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    <p>I am trying to understand tagged types and code extensions and reuse. I first create a program <code>conventional_method_number_of_averages</code> which implements one method for doing some calculation. Then I use extension of the tagged type and create a second program <code>alternative_method_number_of_averages</code> which implements a different method for solving the same problem. The difference is that now I have an additional <code>parameter</code>called <code>overlap_fraction</code>. Here is the simple program with the first method <code>conventional_method_number_of_averages</code> that works fine:</p> <ol> <li><p><strong>number_of_averages.ads</strong></p> <pre><code>with Conventional_Method_Number_Of_Averages; package Number_Of_Averages renames Conventional_Method_Number_Of_Averages; </code></pre></li> <li><p><strong>conventional_method_number_of_averages.ads</strong></p> <pre><code>package Conventional_Method_Number_Of_Averages is type First_Method is tagged private; procedure Count_Averages (Any_Method : in out First_Method; Sampling_Frequency, FFT_Size, Time_Recorded: in Float); function Average_Is (Any_Method : in First_Method) return Float; private type First_Method is tagged record Number_Of_Averages : Float :=0.0; end record; end Conventional_Method_Number_Of_Averages; </code></pre></li> <li><p><strong>conventional_method_number_of_averages.adb</strong></p> <pre><code>package body Conventional_Method_Number_Of_Averages is procedure Count_Averages (Any_Method : in out First_Method; Sampling_Frequency, FFT_Size, Time_Recorded: in Float) is begin Any_Method.Number_Of_Averages := (((Sampling_Frequency * Time_Recorded) - FFT_Size)*(2.0/FFT_Size)) + 1.0; end Count_Averages; function Average_Is (Any_Method : in First_Method) return Float is begin return Any_Method.Number_Of_Averages; end; end Conventional_Method_Number_Of_Averages; </code></pre></li> <li><p>and the test file <strong>test_number_of_averages.adb</strong></p> <pre><code>with Ada.Float_Text_IO; with Ada.Text_IO; use Ada.Text_IO; with Number_Of_Averages; with Conventional_Method_Number_Of_Averages; use type Number_Of_Averages.First_Method; procedure Test_Number_Of_Averages is Fs, Time_Duration, NFFT : Float := 0.0; Averages : Float := 0.0; Good_Method : Conventional_Method_Number_Of_Averages.First_Method; begin Ada.Text_IO.Put("Enter the sampling frequency "); Ada.Float_Text_IO.Get (Item =&gt; Fs); Ada.Text_IO.New_Line (1); Ada.Text_IO.Put("Enter the time recorded "); Ada.Float_Text_IO.Get (Item =&gt; Time_Duration); Ada.Text_IO.New_Line (1); Ada.Text_IO.Put("Enter the FFT size "); Ada.Float_Text_IO.Get (Item =&gt; NFFT); Ada.Text_IO.Put_Line (Ada.Text_IO.Get_Line); Ada.Text_IO.New_Line(1); Ada.Text_IO.Put("Number of averages = "); Number_Of_Averages.Count_Averages(Good_Method, Fs, NFFT, Time_Duration); Averages := Conventional_Method_Number_Of_Averages.Average_Is(Good_Method); Ada.Float_Text_IO.Put (Item =&gt; Averages, Fore =&gt; 3, Aft =&gt; 5, Exp =&gt; 0); end Test_Number_Of_Averages; </code></pre></li> </ol> <p>The above works fine as it is.</p> <p>Now if I create an alternative method for the same calculation, I have:</p> <ol> <li><p>its specification <strong>alternative_method_number_of_averages.ads</strong></p> <pre><code>with Conventional_Method_Number_Of_Averages; use Conventional_Method_Number_Of_Averages; package Alternative_Method_Number_Of_Averages is type Second_Method is new First_Method with private; --override this function procedure Count_Averages (Any_Method : in out Second_Method; Sampling_Frequency, FFT_Size, Time_Recorded, Overlap_Fraction: in Float); private type Second_Method is new First_Method with record Overlap_Fraction : Float :=0.5; end record; end Alternative_Method_Number_Of_Averages; </code></pre></li> </ol> <p>and </p> <ol> <li><p>its body <strong>alternative_method_number_of_averages.adb</strong></p> <pre><code>package body Alternative_Method_Number_Of_Averages is --override this function procedure Count_Averages (Any_Method : in out Second_Method; Sampling_Frequency, FFT_Size, Time_Recorded, Overlap_Fraction: in Float) is begin Any_Method.Number_Of_Averages := ((Sampling_Frequency * Time_Recorded) - FFT_Size) / (FFT_Size - Overlap_Fraction * FFT_Size) + 1.0; end Count_Averages; end Alternative_Method_Number_Of_Averages; </code></pre></li> </ol> <p>Then on compiling the specification file, I get the error message:</p> <p>alternative_method_number_of_averages.ads: no selector "number_of_averages" for type "Second_Method" defined at alternative_method_of_averages.ads. The culprit line is:</p> <pre><code> Any_Method.Number_Of_Averages := ((Sampling_Frequency * Time_Recorded) - FFT_Size) / (FFT_Size - Overlap_Fraction * FFT_Size) + 1.0; </code></pre> <p>So how to fix this?</p> <p>In the end I would like to be able to have something like:</p> <pre><code> Number_Of_Averages.Count_Averages(Alternative_Method, Fs, NFFT, Time_Duration, Overlap_fraction); </code></pre> <p>in the test file <strong>test_number_of_averages.adb</strong>, similarly as the working code</p> <pre><code> Number_Of_Averages.Count_Averages(Good_Method, Fs, NFFT, Time_Duration); </code></pre> <p>Thanks a lot...</p> <p><strong>UPDATE</strong></p> <p>So now for the alternative method implementation, I have, renamed <strong>Alternative_Method_Number_Of_Averages.ads/adb</strong> to <strong>Conventional_Method_Number_Of_Averages-Alternative_Method_Number_Of_Averages.ads/adb</strong>. The test file is:</p> <pre><code> with Ada.Float_Text_IO; with Ada.Text_IO; use Ada.Text_IO; with Number_Of_Averages; with Conventional_Method_Number_Of_Averages; use type Number_Of_Averages.First_Method; with Conventional_Method_Number_Of_Averages.Alternative_Method_Number_Of_Averages; procedure Test_Number_Of_Averages is Fs, Time_Duration, NFFT : Float := 0.0; Averages1 : Float := 0.0; Averages2 : Float := 0.0; Good_Method : Conventional_Method_Number_Of_Averages.First_Method; Alternative_Method : Conventional_Method_Number_Of_Averages.Alternative_Method_Number_Of_Averages.Second_Method; begin Ada.Text_IO.Put("Enter the sampling frequency "); Ada.Float_Text_IO.Get (Item =&gt; Fs); Ada.Text_IO.New_Line (1); Ada.Text_IO.Put("Enter the time recorded "); Ada.Float_Text_IO.Get (Item =&gt; Time_Duration); Ada.Text_IO.New_Line (1); Ada.Text_IO.Put("Enter the FFT size "); Ada.Float_Text_IO.Get (Item =&gt; NFFT); Ada.Text_IO.Put_Line (Ada.Text_IO.Get_Line); Ada.Text_IO.New_Line(1); Ada.Text_IO.Put("Number of averages = "); Number_Of_Averages.Count_Averages(Good_Method, Fs, NFFT, Time_Duration); Averages1 := Conventional_Method_Number_Of_Averages.Average_Is(Good_Method); Ada.Float_Text_IO.Put (Item =&gt; Averages1, Fore =&gt; 3, Aft =&gt; 5, Exp =&gt; 0); Ada.Text_IO.New_Line(1); Ada.Text_IO.Put("Number of averages = "); Number_Of_Averages.Alternative_Method_Number_Of_Averages.Count_Averages(Alternative_Method, Fs, NFFT, Time_Duration); Averages2 := Conventional_Method_Number_Of_Averages.Alternative_Method_Number_Of_Averages.Average_Is(Alternative_Method); Ada.Float_Text_IO.Put (Item =&gt; Averages2, Fore =&gt; 3, Aft =&gt; 5, Exp =&gt; 0); end Test_Number_Of_Averages; </code></pre> <p>With Fs = 48000, Time_Duration = 60, NFFT = 8192, both methods are returning 702.125. The second method though is always returning 702.125 irrespective of the <code>Overlap_Fraction</code> parameter. How to specify <code>Overlap_Fraction</code> in the calling function, while still keeping using it private i.e. by having the function use the value of <code>Overlap_Fraction</code> stored in the record.</p>
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