Trying to declare an array from the heap from inside a record declaration

[Jerry <list_email@icloud.com>]

Several years ago a kind and clever person on this list showed me how to allocate possibly large arrays from the heap without breaking functions which expect just normal arrays. Using the Numerics features as an example, it might look like this...

M, N : Integer := 100; -- Included here for clarity.
x_Ptr : Real_Vector_Access := new Real_Vector(M .. N);
    x : Real_Vector renames x_Ptr.all;

... and subprograms which expect a Real_Vector have no problems with this x.

Now, I want to put this kind of thing inside a record declaration, but the compiler complains. I'm trying this:

type foo(M, N : Integer) is
    record
        y : Real_Vector(M .. N);
        x_Ptr : Real_Vector_Access := new Real_Vector(M .. N);
            x : Real_Vector renames x_Ptr.all;
    end record;

y is accepted as OK but the x_Ptr line generates "unconstrained subtype in component declaration" and the next line generates "missing ";"".

Jerry