Re: Amazing

Post #101,710 by admin 5/13/03 5:02:52 PM Reply	Re: Amazing If something is non-existent in APL and you try to refer to it, the interpreter stops (other things being default equal). If you have a null object in Java, and you try to use it, the interpreter stops. Not the same != can't be used the same. I'm really not catching what you're on about here. "If something is non-existent". How do you represent something that is non-existent in APL then? Regards, -scott anderson "Welcome to Rivendell, Mr. Anderson..."
Post #101,715 by deSitter 5/13/03 5:32:07 PM Reply	Re: Amazing It's a very subtle and difficult point. You can't model non-existence with something that exists and has a special value, no matter what it is. So "Set s=null" is emptiness, not non-existence. Strong typing means that everything you refer to HAS to exist. Set s = new HashSet() is not emptiness, because s now has an identifiable property. It's like an empty glass of water - s is the glass, not the water. In APL, an empty array is in an intermediate area - it exists but has no properties. BY DEFINITION, size 0 = empty. So you can safely deal with emptiness because your in no danger of causing an NPE. Here's an example: [link\|http://www.csm.astate.edu/~rossa/cs3543/apl.html\|http://www.csm.astat...a/cs3543/apl.html] I have to run but will get back to this interesting topic. Please, let's bury the hatchet - IN CONRAD! -drl
Post #101,721 by Arkadiy 5/13/03 5:51:19 PM Reply	Wow. My first exposure to APL and Brainfck seems to be not too bad at all. But you are right. APL's empty is closer to Smalltalk's Null than Java's null. Correct me somebody, but I think Smalltalk's Null can be made to behave exactly like APL empty if so desired. E.g. 0nil would now yeild doNotUnderstand exception, but you can handle some messages in Null and in Number to make it evaluate to nil. -- Less Is More. In my book, About Face, I introduce over 50 powerful design axioms. This is one of them. --Alan Cooper. The Inmates Are Running the Asylum
Post #101,726 by admin 5/13/03 6:04:05 PM Reply	Same as in Objective C Regards, -scott anderson "Welcome to Rivendell, Mr. Anderson..."
Post #101,732 by JimWeirich 5/13/03 6:50:46 PM Reply	Re: Amazing deSitter: It's a very subtle and difficult point. Its even more subtle than that. Its not merely empty vs non-empty, but APL doesn't distinguish between a single number and an array of length one.* In other words, the number 1 can be treated as a number, or as an array of a single element. Now this is makes for some convient shortcuts in programming (much like returning a zero when unboxing a null pointer), but I don't think it is mathematically very accurate. In Math, a set of things and a thing are not the same thing. Footnotes: Assuming I correctly remember what little APL I ever knew. Assuming I correctly remember what little set theory I ever knew. * Do I get extra points for using the word thing(s) three times in one sentence? -- -- Jim Weirich jweirich@one.net [link\|http://w3.one.net/~jweirich\|http://w3.one.net/~jweirich] --------------------------------------------------------------------- "Beware of bugs in the above code; I have only proved it correct, not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)
Post #101,750 by tseliot 5/13/03 9:03:03 PM Reply	Heh. *** Do I get extra points for using the word thing(s) three times in one sentence? Only if you publish it as "Thing Theory". :D Many fears are born of stupidity and ignorance - Which you should be feeding with rumour and generalisation. BOfH, 2002 "Episode" 10
Post #101,767 by deSitter 5/13/03 11:09:01 PM Reply	ROFL -drl

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