[CM] some CM sprout/process questions

[Larry Troxler]

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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> >Cmdist@ccrma.stanford.edu
> >http://ccrma-mail.stanford.edu/mailman/listinfo/cmdist
>
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--  Larry Troxler  --  lt@westnet.com  --  Patterson, NY USA  --