Re: Problem with indefinite discriminant records in container

[Simon Wright <simon@pushface.org>]

john@peppermind.com writes:

> How can I store different versions of an indefinite record with
> discriminants such as Rt_Class in some array or vector?

You should be able to do this. I made a compilable program with
mocked-up versions of the omitted types, and it compiles and runs with
every version of GNAT I have here.

with Ada.Containers.Indefinite_Vectors;
procedure John is

   subtype Methodid is Natural range 0 .. 10;
   subtype Classid is Natural range 0 .. 10;
   type Rt_Methods is array (Natural range <>) of Integer;
   type Rt_Class_Ids is array (Natural range <>) of Integer;

   type Rt_Class (Method_Table_Size : MethodId;
                  Superclass_Count  : ClassId)
     is record
        Id              : ClassId;
        Is_Interface    : Boolean;
        Methods         : Rt_Methods (1 .. Method_Table_Size);
        Superclasses    : Rt_Class_Ids (1 .. Superclass_Count);
        Inst_Prop_Count : Natural;
        Method_Count    : Natural;
     end record;

   package Class_Vectors is new Ada.Containers.Indefinite_Vectors
     (Index_Type => ClassId,
      Element_Type => Rt_Class);
   use Class_Vectors;
   type Rt_Classes is new Class_Vectors.Vector with null record;

   C :  Rt_Classes;

begin
   C.Append (Rt_Class'(Method_Table_Size => 1,
                       Superclass_Count => 1,
                       Id => 4,
                       Is_Interface => False,
                       Methods => (1 => 42),
                       Superclasses => (1 => 43),
                       Inst_Prop_Count => 44,
                       Method_Count => 45));
end John;

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On a separate front, it seems to me that

   use Class_Vectors;
   type Rt_Classes is new Class_Vectors.Vector with null record;

are nudging the edge of current GNAT; indexing on the LHS, eg
   C (0) := ...
confused the heck out of the compiler, in differing ways for GNAT GPL
2014 and FSF GCC 4.9.0; something to do with Cursors, I think.