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chuckles
Joined: Apr 02, 2007
Posts: 72
Location: San Diego, California
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 Posted: Mon Jun 04, 2007 9:53 am Post subject:
Latest mystery problem
Subject description: Bug? |
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OK, here's a simple demonstration of something that gives a compile error that I can't figure out. Mandolin and StifKarp are both StkInstruments, yes?
Then why do these statements compile OK:
| Code: | [new StifKarp, new Mandolin ] @=> StkInstrument voice1;
[]; [new Mandolin, new StifKarp ] @=> StkInstrument voice2[]; |
but these give an error message
| Code: | [new StifKarp, new StifKarp ] @=> StkInstrument voice3[];
[new Mandolin, new Mandolin ] @=> StkInstrument voice4[]; |
| Code: | [unnamed2]:line(7): cannot assign '@=>' on types 'Mandolin[]' @=> 'StkInstrument[]'...
[unnamed2]:line(7): ...(reason: --- incompatible types for assignment) |
This can be extended too to more than two instruments. I found out about it by experimenting with the "In C" project where he defines something like 9 instruments which are a mixture of StifKarp and Mandolin. I wondered why he did that and it's apparently because you can't create an array of StkInstruments that are all the same type.
Comments, anyone?
Thanks!
c. |
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spencer
Joined: Aug 16, 2006
Posts: 53
Location: northern california
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| Posted: Mon Jun 04, 2007 4:45 pm Post subject:
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Hey chuckles,
I think ChucK's implicit typing rules force a literal array of objects to be the most specific type/subclass possible while still having them be all the same type at some level. So | Code: | | [new StifKarp, new Mandolin ] @=> StkInstrument voice1; |
is an array of StkInstruments, but | Code: | | [new StifKarp, new StifKarp ] @=> StkInstrument voice3[]; |
is an array of StifKarps. Also, unfortunately, ChucK's typing rules don't allow you to cast an array of a class to an array of its superclass.
Anyways the solution is this: | Code: | | [new Mandolin $ StkInstrument, new Mandolin ] @=> StkInstrument voice4[]; |
This forces ChucK to think that the most specific type that applies to all elements is StkInstrument, so it is an array of StkInstrument rather than Mandolin.
spencer |
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chuckles
Joined: Apr 02, 2007
Posts: 72
Location: San Diego, California
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| Posted: Tue Jun 05, 2007 8:26 am Post subject:
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Thanks so much Kassan, that will make life easier for me, and it also educates me about $ casting...
(Another way to get around the problem, apparently, though not very elegant, would be to explicitly assign like:
| Code: | StkInstrument voice4[2];
new StifKarp @=> voice4[0];
new Mandolin @=> voice4[1]; |
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Kassen
Janitor
Joined: Jul 06, 2004
Posts: 7678
Location: The Hague, NL
G2 patch files: 3
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| Posted: Tue Jun 05, 2007 9:35 am Post subject:
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| chuckles wrote: | | Thanks so much Kassan, |
I'm happy you are happy but (Spencer != Kassen), in fact I haven't yet had the pleasure of meeting Spencer in person.
There's more then one person trying to answer question in the ChucK-scene(and that's a good thing too!).
:¬)
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Kassen |
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chuckles
Joined: Apr 02, 2007
Posts: 72
Location: San Diego, California
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| Posted: Fri Jun 08, 2007 8:34 am Post subject:
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My apologies to both Spencer and Kassen; Spencer for not thanking him for his clarification of my problem, and Kassen for spelling his name wrong! Thanks to both of you for helping out in this forum -- the forest of ChucK has some dark areas and mysterious paths for a beginner...
...c... |
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Kassen
Janitor
Joined: Jul 06, 2004
Posts: 7678
Location: The Hague, NL
G2 patch files: 3
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| Posted: Fri Jun 08, 2007 9:23 am Post subject:
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No harm done, Chuckles. I've had a unusual name for quite a while now and I've been dyslexic for a similar period so i can't blame anyone for spelling.
And, yes, it does, but I think that's half the fun.
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