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Aaron Hall
Aaron Hall
12:13 AM
@JamieMarshall can you point me to this definition from which one could conclude that a sum of hashes is not a hash? I'm not arguing that summing hashes to create your own hash is a great idea here, but it does seem to me to be one way to deterministically create a value that exists for the life of a process where the likelihood of collisions is low. I'm sure that the hash of a tuple of the elements is probably superior in performance in all ways, but I'm still unconvinced of your assertion that a sum of hashes is not itself a hash - to my knowledge, it meets the definition of a hash. — Aaron Hall ♦ 1 min ago
Please someone tell me how I'm wrong and why. ^^^^^^
 
 
2 hours later…
Computer Science Meta
Computer Science Meta
2:21 AM
0
Q: What to do if your best questions are getting downvoted?

Travis WellsRecently, I have asked a question and made sure that I provided enough details showing that I somewhat understand what I'm reading. Overall, what details should be omitted that make the question easier to understand? Question link

discussion support
 
 
7 hours later…
Discrete lizard
Discrete lizard
9:22 AM
@AaronHall You have the right definition of a hash. However, informally, people often mean a good hash function when talking about a hash. Anyway, I've replied to the comment thread.
 
 
5 hours later…
Aaron Hall
Aaron Hall
2:01 PM
@Discretelizard thanks.
 
 
7 hours later…
Micrified
Micrified
8:59 PM
I've got a question concerning the definition of a First set. My course resources explain that a First-set may be computed using the following rules. When analyzing the following example grammar: 
S -> E x
E -> y
E ->
I would say that First(E) = {y, epsilon}, and then by rule (4), that it becomes First(E) = {y, epsilon} \ {epsilon} Union First(x) which is then {y,x}
Because E produces epsilon, and is followed by terminal x in the first production.
Yet if I try a tool like Grammophone online, it tells me that the first set is simply {y, epsilon}.
(for production E)
When I try to think of what symbols may appear at the beginning of a sentence derived from E, it seems wrong to say that x can appear, since it is derived from S. Yet my course resources make this rule.
Well, perhaps I misunderstood. And that the rule represents the first-set of the "combined" production (X alpha) where in this case you would include x. Think I just explained the answer to myself when writing it ...
 

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