Worn out from complaining too aggressively
There is a lot I draw from this.
First off, people aren't replying to him on the email list. I find this incredibly lame because I believe, regardless of how he is raising it, that he raises a legitimate point that will cause consternation among people.
The basic thing is that:
user> (= (list 2 3) [2 3])
true
user> (hash (list 2 3))
-1919631535
user> (hash [2 3])
1026
user>
'=' semantics do not match hash semantics exactly. This means that if you intermix lists and vectors as keys in a hash map then you are going to get really odd results:
user> { [2 3] 4 (list 2 3) 5 }
{[2 3] 4, (2 3) 5}
user> (filter (= [2 3] %) (keys *1))
; Evaluation aborted.
user> (filter #(= [2 3] %) (keys *1))
([2 3] (2 3))
user>
You might ask how one would get into this situation, but you will get into it in some subtle ways. For instance you would (map identity [2 3]) and the result would be equal to [2 3] but it wouldn't be the same key in a hash-map.
I personally, now that I know about this, have absolutely no problem working around it. People who are used to c++ have had to work around much, *much* worse (like today I worked around a heap corruption problem that caused a failure in an unrelated piece of code).
People who are used to Java are used to a *completely* normalized environment. This is the ideal that we all strive for; no idiomatic problems that you have to deal with; just pure mathematical consistency. And perhaps a comfortable death of carbon monoxide.
I have never seen anything really cool that is that vanilla. Try using opengl in some advanced case; use c++ for a serious task (and succeed), play with CUDA. Badass tech makes sacrifices and sometimes these sacrifices are exactly in some area that causes serious problems. It is like really good scotch; you have to come to it and just take it for what it is. Judge it because it fails to wipe your ass for you and you miss out on some really fucking awesome engineering.
I think that Rich should probably fix this. But if he doesn't it is a problem that I can trivially work around. I would *much* rather use clojure because I think it is a super fun system to play with and I know that I can work around anything it throws at me, no question. I did it with .NET, I have done it with c++, I can trivially do it with the JVM and clojure.
Abstractions have leaks. And the really good abstractions still have really painful leaks. Learn them, understand them, and move on. Save the judgement for someone who cares.
Chris
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2 comments:
I don't know, I find this kind of thing to be more of an annoying complaint from a wanker than anything else. In general I would typically consider it bad form to be mixing lists and vectors in a hash-map anyway. Just because you can operate over various types of collections using the Seq interface, I don't think it's correct to think of them as being the same thing. To me it seems like the = should not be the same before changing the way hash identity works. Anyway, this is something I'm doubtful I'd ever run up against.
First off, people aren't replying to him on the email list. I find this incredibly lame because I believe, regardless of how he is raising it, that he raises a legitimate point that will cause consternation among people.
Well, he created an issue as well, and blogged about it. This is too much. People should report problems and have a little patience.
In any case, the issue was fixed and the fix reported via the issue system. I can't reply in 3 forums about the same thing.
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