Ada Array store unbounded String getting from .txt

问题:

Im having a trouble storing unbounded string to an array if I'mm getting it to .txt file. Here is my hardcoded data:

Data : An_Array := (1 => (Name => +"9 - Joe"),
                    2 => (Name => +"8 - Trisha "),
                    3 => (Name => +"7 - RR "),
                    4 => (Name => +"6 - Jane "),
                    5 => (Name => +"5 - Doe "));

What if I want to get the data from a .txt file?

with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;
with Ada.Text_IO;           use Ada.Text_IO;

with Ada.Containers.Generic_Array_Sort;

procedure Main is

   function "+" (S : String) return Unbounded_String renames To_Unbounded_String;

   type A_Composite is
      record
         Name  : Unbounded_String;

      end record;

   function "<" (L, R : A_Composite) return Boolean is
   begin
      return L.Name < R.Name;
   end "<";

   procedure Put_Line (C : A_Composite) is
   begin
      Put_Line (To_String (C.Name));
   end Put_Line;

   type An_Array is array (Natural range <>) of A_Composite;

   procedure Sort is new Ada.Containers.Generic_Array_Sort (Natural, A_Composite, An_Array);

   Data : An_Array := (1 => (Name => +"9 - Joe"),
                       2 => (Name => +"8 - Trisha "),
                       3 => (Name => +"7 - RR "),
                       4 => (Name => +"6 - Jane "),
                       5 => (Name => +"5 - Doe "));
begin
   Ada.Text_IO.Open (File => File,
                     Mode => Ada.Text_IO.In_File,
                     Name => "highscore.txt");

   while not Ada.Text_IO.End_Of_File (File) loop
         declare
            Line :String := Ada.Text_IO.Get_Line (File);            
         begin

              -- get data from .txt and I want it to sotre to Data : An_Array
            end;
   end loop;
   Ada.Text_IO.Close (File);

   Sort (Data);
   for I in Data'Range loop
      Put_Line (Data (I));
   end loop;
end Main;

回答1:

In Ada, any particular array has a fixed length; your Data has a length of 5, even though your type An_Array can be used to declare arrays with any length you like (within reason! your computer only has a fixed amount of memory).

I’m guessing that you want to deal with files where you don’t know beforehand how many lines there are.

You could do this by declaring

Data : An_Array (1 .. 1000);

and keeping a count of how many entries you’ve used:

   Last : Integer := 0;  -- in case the file contains no lines!
begin
   while not Ada.Text_IO.End_Of_File (File) loop
      Last := Last + 1;
      Data (Last) :=
        (Name => Ada.Strings.Unbounded.To_Unbounded_String
           ((File)));
  end loop;

and when the loop ends Data (1 .. Last) contains your data (Data (Last + 1 .. 1000) contains empty strings).

But what if there are 1001 entries in your file?

You could try Ada.Containers.Vectors (ARM A.18.2) and Ada.Containers.Generic_Sort (ARM 18.29(9.1)) - you’d have to work out how to specify Before, and to write your own Swap procedure.

回答2:

Inserting an Unbounded_String in an array of Unbounded_Strings is trivial:

An_Array (3) := An_Unbounded_String;

But is that your actual problem?