> OK, interesting - it wouldn't be a huge task, but why is this a good idea? > It just seems inconvienient for the recipient and I dont know of any other > RPC mechanisms where its allowed (or wanted). In the case of typetag-less > messages it would be difficult to handle, you'd have to try to discover > the type of the argument by inspection. Do you have a link to a rationale > for this?
Firstly, from the horses mouth, "non-type-tagged messages [are] totally deprecated". See <http://www.create.ucsb.edu/pipermail/osc_dev/2003-November/00032 9.html> and surrounding posts. I don't think you need to even try to think about possibly considering perhaps partially supporting such things! Secondly, it is actually no work for the receiver. The receiver says that is needs a signed 32bit integer and it gets such an integer. It is a little work for the library. On the other hand it can be a lot of work for the sender. Domain specific languages often do not implement full C like numerical towers, a signal processing language could easily only implement floating point numbers, Lua famously has only double precision floating point numbers, and lots of people use Lua. Since I think this is really important I will give an example, and from the other end of a continuum. I use scheme for most of my music work. Scheme has a very sophisticated numerical tower. I might write (-> "/n_set" 1001 "freq" 440) to set the frequency of an instrument at SC3. The OSC encoder encodes values based on their lisp type, 1001 is an integer and gets encoded as 'i'. Lets assume that to the receiver the frequency argument is a float, here I lose because 440 is an integer. I argue that a receiver implemented like that is just wrong, that an integer 440 frequency is completely valid, and SC3 thankfully agrees and plays the right note. However if you disagree and say that I should write the literal as a float then that makes scheme a hopeless language to work in, 440.0 is still an exact integer, I need to write #i440 to get an inexact integer. But the situation is far worse, if I write (* m 1.5) this seems like it should make an inexact value regardless where m arrives from, however scheme knows that (* 0 1.5) is an exact zero and I lose again, it may even know that (* 2 1.5) == (* 2 3/2) == 3, an exact integer . Forcing a user to _very_ carefully annotate _all_ code that might get sent as an OSC packet _only because_ the OSC receiver cannot accept exact integers is not going to work, I just won't be able to work with the process. SC3 gets this very right, as usual, and in fact allows: (-> "/n_set" #i1000 (exact->inexact 0) 440) The node and index values at SC3 are syntactically integers (the index can also be a string name that maps to an integer), and the argument is syntactically a float, but it accepts floating point encodings of integers and integer encodings of real values. SC3 does it like this, QED :) > I agree that combining the verb and subject seems a little odd, but that > is the sitatuion in the web services world too - when neccesary they get > round it by adding a verb argument eg ("/my/path", "verb", ...), which is > a useful cnvention but its not neccesary to set it in stone. I think the real question is, does anyone really want to do pattern matching on the operator? I have never seen a convincing example. It would introduce all sorts of really strange sequencing issues to start with... The pattern matching people seem to like is usually of the form ("/instr[1-4]/freq" 440), not ("/instr1/{freq,ampl}" 330). If you restrict the matching to the subject, make the subject an argument, and make the operator the OSC address then the OSC dispatch mechanism can be reasonably efficient, which matters in RT synthesis environments, and people who want RE descriptors for subjects can do that without imposing an onerous burden on the core dispatch mechanism. And it looks better! In fact it looks comfortingly like lisp, ("/freq" "/instr[1-4]" 550) :-\ > > * not allocate any memory or call any other non-RT safe procedure > This one is inherantly not possible, youre doing i/o operations. Well actually it is only doing the byte encoding. SC3, being dragged out for yet another example, allows users to link in the synthesis engine and push OSC packets directly onto a queue, thus avoiding any IPC operations but still using an identical communication protocol. For the liblo case you are of course correct, but the temporal behaviour of the encoder/decoder can be pretty predictable. > I've always been more of a strongly-typed guy :) Me too, we schemers all are, we just think that an exact integer is a real number :) Regards, Rohan
