Re: A simple ADA puzzle (I haven't the answer)

[Hyman Rosen <hyrosen@mail.com>]

Frank J. Lhota wrote:
> The part that I find completely counterintuitive is how anyone can expect to
> write a simple record type that, without any additional memory allocation,
> could hold arbitrarily large arrays and still remain within reasonable
> memory constraints.

Because when you write

     type STRING_TYPE (LEN : INTEGER := 0) is
       record STRING : LEN_TYPE (1 .. LEN); end record;

it's perfectly reasonable to expect that the array is
allocated just enough room to hold whatever LEN is
specified. After all, you can do something that looks
superficially very similar (or at least I think so; I
don't know Ada):

     procedure foo(LEN : INTEGER) is
       type LEN_TYPE is array (INTEGER range <>) of CHARACTER;
       type STRING_TYPE is
         record STRING : LEN_TYPE (1 .. LEN); end record;
       X : STRING_TYPE;
     begin end foo;

and this is perfectly fine, and will only allocate LEN
elements. Now, all the experts here certainly understand the
difference, and even I do, but what is a newcomer to Ada to
make of this?