Self-interest September 2002

self-interest@lists.selflanguage.org

4 participants
3 discussions

embedding based prototype languages
by James McCartney 13 Nov '02

13 Nov '02

Is there a list for discussing prototype languages in general? I am interested in figuring out some details concerning languages like Omega, Kevo, Obliq that prefer embedding over delegation. The idea of embedding never really made sense to me until I read some slides by Luca Cardelli ("Object based vs Class based Languages", PLDI 96 Tutorial). Some things still seem problematic with the approach. I like a few things about it, easy to make dispatch fast, objects are self sufficient. For me, fast dispatch is important since I am currently using a Smalltalk-like language with constant time dispatch. It seems that change management would be a nightmare when you want to update a method that was inherited by a lot of objects. This might be solved by using "become:" ?? The slides contain this quote: "In embedding based languages such as Kevo and Omega, pervasive changes are achieved even without donor hierarchies." How? Also it seems more difficult to use inheritance in certain "part-of" situations (as was done NewtonScript for example), or doing so would cause a lot of unecessary space usage. This quote is also there: "Super and override make sense for implicit inheritance but not for explicit inheritance." But don't you still need to call the 'super' method in the (explicitly) overriding method sometimes? Another observation is that if you have doesNotUnderstand: then it is trivial to reimplement parent delegation in an embedding only language. So why not build it in to the dispatch routine anyway? I can't seem to find any info at all on the web on Kevo other than brief mentions. Omega seems very out of date. I'm unsure of the status of Obliq. -- --- james mccartney james(a)audiosynth.com <http://www.audiosynth.com> SuperCollider - a real time synthesis programming language for the PowerMac. <ftp://www.audiosynth.com/pub/updates/SC2.2.16.sea.hqx>

5 21

bugs in sparc VM
by Jecel Assumpcao Jr 01 Oct '02

01 Oct '02

After looking for bugs in my code for a couple of days I came to the conclusion that the compiler might be generating bad code (which shows how humble I have become - back in the Burroughs Algol days I always blamed the compiler first ;-) In one case I have something like [add: addr+1. test: (memory at: addr)] whileFalse. and the loop kept going right past the iteration where 'test:' returned true. Running the same thing step by step in the debugger worked. Finally I decided to save a snapshot, quit the VM, restart everything and then this started working. In another case I have word: (memory at: addr) && 16r0FFFF. and I verified that "memory at: addr" is returning 16r01515 yet word is being assigned 16r0FFFF. Single stepping makes it work. The save/restore trick I used above didn't work in this case. In fact, eliminating the "halt" and allowing it to continue after having single stepped this a few times showed that it worked until it exited the inner loop and then it went back to the broken behavior. So I would guess that the NIC is generating correct code but the SIC isn't. The obvious next step is to disable the SIC and see what happens, but I will only be able to do that on Friday. This is the 4.1.5 VM on a Ultra 5 running Solaris 2.8. -- Jecel

2 4

inheritance in Self
by Steve Dekorte 19 Sep '02

19 Sep '02

Do I have this right?: 1. The Object proto delegates to the Lobby (so lookup for "globals" in objects inheriting from the Object proto get found) 2. The Lobby is an instance of an Object(so it can deal with messages like "respondsTo:" etc) If so, how are lookup loops avoided? (Something not found in the Object proto goes to the lobby, isn't found there so it gets sent to the Object proto) Cheers, Steve

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Self-interest September 2002