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Can someone explain the traverse function in Haskell?
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traverse is the same as fmap, except that it also allows you to run effects while you're rebuilding the data structure.
Take a look at the example from the Data.Traversable documentation.
data Tree a = Empty | Leaf a | Node (Tree a) a (Tree a)
The Functor instance of Tr...
How to keep a .NET console app running?
... a Console application that starts up some services in a separate thread. All it needs to do is wait for the user to press Ctrl+C to shut it down.
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Javascript - removing undefined fields from an object [duplicate]
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You actually don't even need the ternary operator. Instead you can do (obj[key]===undefined&& delete obj[key]) The reason this works is because and uses short-circuit evaluation, so once the first check fails the second isn'...
How do I use cascade delete with SQL Server?
...o perform cascading delete in SQL Server when a record from T1 is deleted, all associated records in T2 also deleted.
8 An...
Change auto increment starting number?
In MySQL, I have a table, and I want to set the auto_increment value to 5 instead of 1 . Is this possible and what query statement does this?
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Block Comments in Clojure
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Actually, there is a way!
(comment
(defn hey []
("Hey there!"))
Check me out!
)
Just wrap your comments in (comment ..) :)
Have fun!
share
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Calling a function when ng-repeat has finished
What I am trying to implement is basically a "on ng repeat finished rendering" handler. I am able to detect when it is done but I can't figure out how to trigger a function from it.
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Which is faster in Python: x**.5 or math.sqrt(x)?
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I've now run it 3 times on codepad.org and all three times a() was much faster than b().
– Jeremy Ruten
Nov 29 '08 at 1:38
13
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Difference between std::result_of and decltype
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result_of was introduced in Boost, and then included in TR1, and finally in C++0x. Therefore result_of has an advantage that is backward-compatible (with a suitable library).
decltype is an entirely new thing in C++0x, does not restrict only to return type of a function, and is a language fe...
Apply multiple functions to multiple groupby columns
...ion.
I recommend making a single custom function that returns a Series of all the aggregations. Use the Series index as labels for the new columns:
def f(x):
d = {}
d['a_sum'] = x['a'].sum()
d['a_max'] = x['a'].max()
d['b_mean'] = x['b'].mean()
d['c_d_prodsum'] = (x['c'] * x['d...