Re: S-expression I/O in Ada

[Natacha Kerensikova <lithiumcat@gmail.com>]

On Aug 12, 10:45 pm, Ludovic Brenta <ludo...@ludovic-brenta.org>
wrote:
> The other notations:
>
> (tcp-connect ((host foo.example) (port 80)))
>
> and
>
> (tcp-connect (host foo.example) (port 80))
>
> are shorthand for that.

What bother me in this is that I feel those are two different objects.

I won't go into writing explicit cons pairs again, this is quite
unreadable. So I'll go for an ASCII-art representation, I hope it
won't be scrambled (if so please tell me, I'll try to come up with a
textual representation). Let L and A represent nodes, respectively
lists and atoms, vertical lines for "next in list", "brother" or
"cons" relations, and horizontal lines for "first child of list" or
"atom contents" relations.

Consider these two objects:

L--A--tcp-connect
   |
   L--A--host
   |  |
   |  A--foo.example
   |
   L--A--port
      |
      A--80

and:

L--A--tcp-connect
   |
   L--L--A--host
      |  |
      |  A--foo.example
      |
      L--A--port
         |
         A--80

I'm sure we can agree on the fact that these are two different and non-
equivalent objects: not the same topology and not even the same number
of nodes. So I'd say a proper S-expression library has to be able to
deal with both of them without mixing them up.

However, by considering as equivalent the two representations quoted
above, I'm afraid you might mixing these two object during encoding or
decoding.

Or have I misunderstood again?



Natacha