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How does deriving work in Haskell?
Algebraic Data Types (ADTs) in Haskell can automatically become instances of some typeclasse s (like Show , Eq ) by deriving from them.
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How to exit from Python without traceback?
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If sys.exit() is called in "main program stuff", the code above throws away the value passed to sys.exit. Notice that sys.exit raises SystemExit and the variable "e" will contain the exit code.
– bstpierre
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Scala: List[Future] to Future[List] disregarding failed futures
...ures to a Future of List. I'm using Playframework, so ultimately, what I really want is a Future[Result] , but to make things simpler, let's just say Future[List[Int]] The normal way to do this would be to use Future.sequence(...) but there's a twist... The list I'm given usually has around 10-...
Convert any object to a byte[]
... }
}
Note that obj and any properties/fields within obj (and so-on for all of their properties/fields) will all need to be tagged with the Serializable attribute to successfully be serialized with this.
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Debugging in Clojure? [closed]
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There's also dotrace, which allows you to look at the inputs and outputs of selected functions.
(use 'clojure.contrib.trace)
(defn fib[n] (if (< n 2) n (+ (fib (- n 1)) (fib (- n 2)))))
(dotrace [fib] (fib 3))
produces the output:
TRACE t4425: (f...
Swift Beta performance: sorting arrays
...t))
// [-1, 0, 2, 2, 5, 8, 1234]
// [-1, 0, 2, 2, 5, 8, 1234]
Both are called in the same program as written.
var x_swift = CInt[](count: n, repeatedValue: 0)
var x_c = CInt[](count: n, repeatedValue: 0)
for var i = 0; i < n; ++i {
x_swift[i] = CInt(random())
x_c[i] = CInt(random())
}...
Mongoose populate after save
I cannot manually or automatically populate the creator field on a newly saved object ... the only way I can find is to re-query for the objects I already have which I would hate to do.
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Regular expression to find URLs within a string
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It's 2017, and unicode domain names are all over the place. \w may not match international symbols (depends on regex engine), the range is needed instead: a-zA-Z0-9\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF.
– Michael Antipin
Aug...
What is the difference between old style and new style classes in Python?
...(x) is always <type
'instance'>.
This reflects the fact that all old-style instances, independently of
their class, are implemented with a single built-in type, called
instance.
New-style classes were introduced in Python 2.2 to unify the concepts of class and type.
A new-s...
How do I add multiple arguments to my custom template filter in a django template?
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It is possible and fairly simple.
Django only allows one argument to your filter, but there's no reason you can't put all your arguments into a single string using a comma to separate them.
So for example, if you want a filter that checks if variable X is in the list [1...