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What does “coalgebra” mean in the context of programming?
I have heard the term "coalgebras" several times in functional programming and PLT circles, especially when the discussion is about objects, comonads, lenses, and such. Googling this term gives pages that give mathematical description of these structures which is pretty much incomprehensible to me. ...
Why can't overriding methods throw exceptions broader than the overridden method?
I was going through SCJP 6 book by Kathe sierra and came across this explanations of throwing exceptions in overridden method. I quite didn't get it. Can any one explain it to me ?
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Java synchronized method lock on object, or method?
If I have 2 synchronized methods in the same class, but each accessing different variables, can 2 threads access those 2 methods at the same time? Does the lock occur on the object, or does it get as specific as the variables inside the synchronized method?
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PostgreSQL delete with inner join
...
DELETE
FROM m_productprice B
USING m_product C
WHERE B.m_product_id = C.m_product_id AND
C.upc = '7094' AND
B.m_pricelist_version_id='1000020';
or
DELETE
FROM m_productprice
WHERE m_pricelist_version_id='1000020...
Joining three tables using MySQL
I have three tables named
8 Answers
8
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how to check if object already exists in a list
...eeds of the specific situation. For example, the dictionary approach would be quite good assuming:
The list is relatively stable (not a lot of inserts/deletions, which dictionaries are not optimized for)
The list is quite large (otherwise the overhead of the dictionary is pointless).
If the above ...
Python Dictionary to URL Parameters
...ictionary to a string for use as URL parameters. I am sure that there is a better, more Pythonic way of doing this. What is it?
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What's the difference between & and && in MATLAB?
What is the difference between the & and && logical operators in MATLAB?
7 Answers
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Append an object to a list in R in amortized constant time, O(1)?
If I have some R list mylist , you can append an item obj to it like so:
17 Answers
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How to implement a queue with three stacks?
I came across this question in an algorithms book ( Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne).
5 Answ...