Re: set_index and and end_of_file with just a stream reference

[Shark8 <onewingedshark@gmail.com>]

On Saturday, February 20, 2021 at 12:08:16 PM UTC-7, 0012com wrote:
> Okay :-) 
> what I wanted is: 
> I read an acronyme in the stream file, if good I input the adjacent record type, otherwise I would advance on the stream until the next acronyme with set_index(stream_access, index(stream_access) + composite_type_stream_size) and read the next acronyme (unbounded_string). 
> Now I just input both objects and verify the acronyme. 
> But I don't like writing an object that maybe won't be used.
Hm, what are your datatypes? Is this ONLY text, or are you able to impose your own structure?
You could have something like this:

-- Instantiated Container Packages.
Package String_Holder is new Ada.Containers.Indefinite_Holders(
       Element_Type => String,
       "="          => Ada.Strings.Equal_Case_Insensitive
      );
Package String_Map is new Ada.Containers.Indefinite_Ordered_Maps(
       "<"          => Ada.Strings.Less_Case_Insensitive,
       "="          => Ada.Strings.Equal_Case_Insensitive,
       Key_Type     => String,
       Element_Type => String
      );

-- The heart of the operating program.
With String_Holder, String_Map;
Package Acronyms is
  -- Because this is it's own type, you can put other things in the record, like a link to the place that it's defined, if needed.
  Type Initialism is new String_Holder.Holder with null record;

  Function Expand( Acronym : Initialism ) return String;
  Procedure Register( Acronym, Expansion : String );
--...
End Acronyms;

Package Body Acronyms is
    Acronym_Map : String_Map.Map;
  Procedure Register( Acronym, Expansion : String ) is
  Begin
    Acronym_Map.Insert( New_Item => Expansion, Key => Acronym );
  End Register;  

  Function Expand( Acronym : Initialism ) return String is
  Begin
    Return Acronym_Map( Acronym );
  Exception
    when others => Return Acronym; -- I forget if it's CONSTRAINT_ERROR or ASSERT_ERROR when the element is not present.
  End Expand;
End Acronyms;

-- in your main Acronym-Stream package...
-- Text_Soup is a variant record for handling portions of an acronym-expanding string; your main data-structure would probably be an Indefinite_Vector of Text_Soup'Class,
-- you might not need Input or output, depending on your usage, but for automatically expanding the initialism you'd need to use Acronyms.Expand.

    Type Text_Soup(<>) is tagged private;
    procedure Output(
       Stream : not null access Ada.Streams.Root_Stream_Type'Class;
       Item   : in Text_Soup'Class);
    function Input(
       Stream : not null access Ada.Streams.Root_Stream_Type'Class)
       return Text_Soup'Class;

   -- Other public operations.
PRIVATE
    For Text_Soup'Class'Input  use Input;
    For Text_Soup'Class'Output use Output;

Type Text_Soup(Length : Natural) is record
  case Length is
    when 0 => Acronym : Initialism;
    when others => Text : String(1..Length);
  end case;
end record;
--...