[CM] some CM sprout/process questions

[Michael Klingbeil]

Interesting error. I don't have access to CMUCL on Linux, so I can't 
really test this. I think this is an issue Rick Taube or others could 
look into.

For the moment you could just redefine copy-object, replacing 
allocate-instance with make-instance. I think the idea was that by 
calling allocate-instance, object initialization is bypassed (thus 
avoiding any possible side-effects), thus allowing the source object 
to be directly "cloned."

But for the purposes of CM, this should be fine:

(defmethod copy-object ((object standard-object))
    (let* ((class (class-of object))
           (new (make-instance class)))
      (fill-object new  object)
      new))


The other way is to just initialize all slots in the new maco

  (setf foo (new i ins 1 time 1.45 duration 4.2))

I hope these suggestions are helpful.


>Greetings, Micheal. It seem that it's allocate-instance that's somehow
>undefined. The following is with CM 2.3.4, on Linux Cmucl:
>
>
>* (setf foo (new i))
>
>#e(i)
>* (setf bar (copy-object foo))
>
>
>No matching method for the generic-function #<Standard-Generic-Function
>ALLOCATE-INSTANCE (3)
>                                               {281B4229}>,
>when called with arguments (#<STANDARD-CLASS I {282AB2AD}>).
>
>On Fri, 27 Sep
>2002, Michael Klingbeil
>wrote:
>
>>  It sounds like each time you are calling 'sv' on your object 'o', you
>>  are overwriting the old slot values. This is one of those examples
>>  where the functional programmers will shout "side effects are bad!"
>>  This isn't a problem if you are immediately sending events out the
>>  midi-port, but if you are putting them into a seq or something like
>>  that, then you need a new object for each event.
>>
>>  Your idea of using copy-object is definitely on the right track and
>>  in fact it should work. Copy-object should work for any kind of CLOS
>>  object... I have used it for stuff not even CM related. What kind of
>>  error are you getting when you attempt to use copy-object? What
>>  version of CM do you have? Maybe there is an old bug?
>>
>>  What I often do to avoid any of this is something like
>>
>>	(output (new csound-event-subclass ...))
>>
>>  just setting the slot values in each output statement. If this is
>>  tedious, then copy-object should (ideally!) do the trick.
>>
>>  You can avoid using defprocess entirely and just insert events into a list:
>>
>>  (setf my-events
>>      (list (new csound-event-subclass ...)
>>            (new csound-event-subclass ...)
>>            (new csound-event-subclass ...)
>>          ...))
>>
>>  (events my-events "mypiece.sco" 0 ...)
>>
>>
>>
>>
>>
>>  >My goal is that I would to sprout a short (say three or four) sequence
>>  >of csound score events.
>>  >
>>  >I thought that rather than hassle with patterns, it would be simpler and
>>  >easier to read, if I can simply write a handfull of sv's and output's
>>  >linearly, so to speak.
>>  >
>>  >For example,
>>  >
>>  >(defprocess note ()
>>  >   (let (o (new csound-event-subclass ...))
>>  >      process repeat 1 do
>>  >        (sv o ...)
>>  >        (output o)
>>  >        (sv o ...)
>>  >        (output o)
>>  >        (sv o ....)
>>  >        (output o)
>>  >         wait 4))))
>>  >
>>  >With this process I intend to define a conceptual "note" that is a short
>>  >sequence of csound events (in this particular case, using a negative p3
>>  >on all but the last event).
>>  >
>>  >In this situation, I want to create an object "o" in the let
>>  >initialization and define the values of most of the slots. In the "sv"'s
>>  >I will modify only one or two of the slots.
>>  >
>>  >I tried the above method both by setting the time slot in the "sv"
>>  >functions, and by providing the optional start-time parameter to the
>>  >"output" functions.
>>  >
>>  >The problem is that it seems that the "sv" calls happen all at once, so
>>  >what happens is that the second and third outputs both get the final
>>  >(third) values of the slots.
>>  >
>>  >I then tried using "copy-object" to use a seperate clone an instance of
>>  >the prototype csound object before modifying it for each output, but for
>  > >some reason the "copy-object" method ends up being undefined for my
>>  >csound event subclass.
>>  >
>>  >Questions:
>>  >
>>  >1. Is there a better idiom for this type of thing? In particular, it
>>  >seems awkward to have to define a process using "repeat 1" for this.
>>  >
>>  >2. What doesn't the default copy-object method work? Do I really need to
>>  >define one for every csound subclass? I would think that copy-object by
>>  >default would simply copy all the slots, but is this not the case?
>>  >
>>  >
>>  >Regards
>>  >
>>  >Larry
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>>
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>
>--  Larry Troxler  --  lt@westnet.com  --  Patterson, NY USA  --