S-expression I/O in Ada
in [ADA]
|
Prev: GPRbuild compatibility
Next: Irony?
From: Shark8 on 13 Aug 2010 11:58 On Aug 13, 2:56 am, Natacha Kerensikova <lithium...(a)gmail.com> wrote: > On Aug 13, 1:26 am, Shark8 <onewingedsh...(a)gmail.com> wrote: > > > I took a bit of a stab at writing an SExpression handler, note that > > it's not a parser [text-file -> SExpression] but rather what (I think) > > you were terming in-memory. > > Indeed, that's what my idea of my still-unnamed in-memory S-expression > object package would look like. > > What I find surprising is that you seem to include type information in > the Node type (which actually represent a S-expression atom, while S- > expression nodes usually include lists too). Is it a typical Ada way > of doing it? > > I find it surprising because the underlying S-expression format (as > standardized by Rivest, I know almost nothing about cons pairs or > lisp) cannot encoding that information. I would expect a S-expression > object in memory to reflect only what can be encoded to and decoded > from S-expression files. > > In fact, one can consider S-expressions as a heterogeneous container, > in that each atom can represent an object of any type (while losing > the type information, which has to be retrieved from somewhere else), > in contrast to thing like vectors, whose items are all of the same > type. Does anybody know an example of heterogeneous container in Ada? > I'm not sure how Ada generics can be leveraged in such a case. > > Another interesting point is that you chose arrays to represent S- > expression lists. Your code seems currently unable to represent empty > lists (which are legal at least in Rivest's S-expressions) but I guess > I can't be too difficult to correct. But it raises the question of > array vs linked list for a S-expression object implementation. > > I'm not sure S-expressions would ever be used in a time-critical > application, so the usual argument of cache-friendliness of arrays is > pretty weak here. S-expressions are meant to be used for I/O where the > bottleneck is most likely to be. > > Ada arrays are statically sized, which can be an issue for parsing, > because S-expression format doesn't encode list length, so a list has > to be built by pushing nodes one after the other until encountering > the end-of-list marker. But I think that should be easily worked > around by using vectors for unfinished S-expression lists, and once > the list is completely parsed build the array from the vector, and > reset the vector for further list parsing. > > However for S-expression objects dynamically created into memory, the > static size of arrays might make some operations much less efficient > than with linked lists. > > Any idea I'm missing about this implementation choice? Would it be > worth to try and make such a package generic over the container type > (array vs linked list vs something else?)? > > Thanks for your code example, > Natacha
From: Jeffrey Carter on 13 Aug 2010 15:23 On 08/13/2010 02:10 AM, Natacha Kerensikova wrote: > On Aug 13, 12:25 am, "Jeffrey R. Carter" > <spam.jrcarter....(a)spam.acm.org> wrote: >> Kerensikova (or is it ?) > > It's both ;-) One of them is my real-life last name, as can be found > on my ID or on copyright notices, while the other is a pseudonymous > last name I've been using over the internet for something like a > decade now. While it was never intended to more than a thin pseudonym, > it was supposed to require a little more research to make the > connection, here I just messed up with Google accounts (I really hate > these browser interfaces, and now it makes me hate them even more, I > wish I could find a NNTP server and a real user-friendly text-mode > news reader). Interesting. IIUC, "-ova" is a Bulgarian feminine patronymic suffix. Port� appears to be French ("carried"). "Natacha" might also be the French transliteration of what is usually transliterated in English as "Natasha". I don't know about a text-mode news reader, but you can point a news reader at freenews.netfront.net without registering. I seem to be getting seriously OT. >> provided a more detailed grammar (using the >> trailing '*' from regexps rather than {}) with some additional options. > > Is one of them more standard than the other? While I'm very familiar > with regex, I only have a few theoretical notions about grammar, and > almost nothing as practical experience with real grammar formats. Both seem to be standards. {} is used in the ARM, Annex P, with its standard meaning of "zero or more", which is why I used it, and am surprised Brenta didn't understand it. > I can assure you what I'm doing is completely conform with Rivest's > standard proposition. I don't know how come it has not reached the > status of full-fledged RFC (while real RFCs like SPKI do depend on > it), but I'm using it as if it had. I only dropped the "display hint" > stuff from the format, because I find it little to no use, while it > introduces quite a bit of complexity. Yes, things are murkier than I realized. S-expressions seem to have originated with Lisp, long before Rivest's proposal, but the cons-pair is an implementation detail, not an inherent part of the syntax, so lists can have zero or more elements. -- Jeff Carter "C++ is like giving an AK-47 to a monk, shooting him full of crack and letting him loose in a mall and expecting him to balance your checking account 'when he has the time.'" Drew Olbrich 52 --- news://freenews.netfront.net/ - complaints: news(a)netfront.net ---
From: Simon Wright on 13 Aug 2010 15:36 Natacha Kerensikova <lithiumcat(a)gmail.com> writes: > (I really hate these browser interfaces, and now it makes me hate them > even more, I wish I could find a NNTP server and a real user-friendly > text-mode news reader). news.eternal-september.org, and emacs.
From: Dmitry A. Kazakov on 13 Aug 2010 15:42 On Fri, 13 Aug 2010 12:23:38 -0700, Jeffrey Carter wrote: > Interesting. IIUC, "-ova" is a Bulgarian feminine patronymic suffix. in all Slavic languages, actually. > "Natacha" might also be the French > transliteration of what is usually transliterated in English as "Natasha". Natasha is Russian's diminutive of Natalia. Compare Sasha-Alexander, Masha-Maria, Pasha-Paul, Grisha-Gregory, Misha-Michael and so on. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de
From: Yannick Duchêne (Hibou57) on 13 Aug 2010 16:44
Le Fri, 13 Aug 2010 21:23:38 +0200, Jeffrey Carter <spam.jrcarter.not(a)spam.not.acm.org> a écrit: > Porté appears to be French ("carried"). Right > "Natacha" might also be the French transliteration of what is usually > transliterated in English as "Natasha". Right too > I don't know about a text-mode news reader, but you can point a news > reader at freenews.netfront.net without registering. I did not knew this one. However, I could also suggest the one I known : nntp.aioe.org/ (or to visit http://www.aioe.org/ ) -- There is even better than a pragma Assert: a SPARK --# check. --# check C and WhoKnowWhat and YouKnowWho; --# assert Ada; -- i.e. forget about previous premises which leads to conclusion -- and start with new conclusion as premise. |