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Tools for analyzing performance of a Haskell program
...gram with +RTS -s
$ time ./A +RTS -s
./A +RTS -s
749700
9,961,432,992 bytes allocated in the heap
2,463,072 bytes copied during GC
29,200 bytes maximum residency (1 sample(s))
187,336 bytes maximum slop
**2 MB** total memory in use (0 MB lost due to frag...
SQL join: selecting the last records in a one-to-many relationship
... MAX(date) MaxDate
FROM purchase
GROUP BY customer_id
) MaxDates ON c.id = MaxDates.customer_id INNER JOIN
purchase p ON MaxDates.customer_id = p.customer_id
AND MaxDates.MaxDate = p.date
The select should join on all custom...
What is the difference between up-casting and down-casting with respect to class variable
...CastException.
To call a superclass's method you can do super.method() or by performing the upcast.
To call a subclass's method you have to do a downcast. As shown above, you normally risk a ClassCastException by doing this; however, you can use the instanceof operator to check the runtime type of...
What is the difference between vmalloc and kmalloc?
...ry about using physically contiguous memory if the buffer will be accessed by a DMA device on a physically addressed bus (like PCI). The trouble is that many system calls have no way to know whether their buffer will eventually be passed to a DMA device: once you pass the buffer to another kernel su...
How to convert SSH keypairs generated using PuTTYgen (Windows) into key-pairs used by ssh-agent and
...hose who get It is required that your private key files are NOT accessible by others error like I had run cd ~/.ssh and chmod 700 id_rsa
– expert
Oct 15 '12 at 17:48
...
Why shouldn't all functions be async by default?
...
If all my code is slowly turning async, why not just make it all async by default?
Well, you're exaggerating; all your code isn't turning async. When you add two "plain" integers together, you're not awaiting the result. When you add two future integers together to get a third future integer ...
How does collections.defaultdict work?
... being thrown, a new entry is created. The type of this new entry is given by the argument of defaultdict.
For example:
somedict = {}
print(somedict[3]) # KeyError
someddict = defaultdict(int)
print(someddict[3]) # print int(), thus 0
...
Rails: Default sort order for a rails model?
...ished => true).
Since Rails 3 you can 'chain' those methods together by concatenating them with periods between them, so with the above scopes you can now use Book.published.confirmed.
With this method, the query is not actually executed until actual results are needed (lazy evaluation), so...
Javascript when to use prototypes
...ing them well is the jQuery library. Every time you obtain a jQuery object by using $('.someClass'), that object has dozens of "methods". The library could achieve that by returning an object:
return {
show: function() { ... },
hide: function() { ... },
css: function() { ... },
animate:...
How to convert an ArrayList containing Integers to primitive int array?
...is:
getting a Stream<Integer> from the list
obtaining an IntStream by mapping each element to itself (identity function), unboxing the int value hold by each Integer object (done automatically since Java 5)
getting the array of int by calling toArray
You could also explicitly call intValue...