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Scala list concatenation, ::: vs ++
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Legacy. List was originally defined to be functional-languages-looking:
1 :: 2 :: Nil // a list
list1 ::: list2 // concatenation of two lists
list match {
case head :: tail => "non-empty"
case Nil => "empty"
}
Of course, Scala evolved other collections, in an ad-hoc manner....
Get last result in interactive Python shell
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Underscore.
>>> 5+5
10
>>> _
10
>>> _ + 5
15
>>> _
15
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Combining two lists and removing duplicates, without removing duplicates in original list
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11 Answers
11
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Code Golf: Collatz Conjecture
Inspired by http://xkcd.com/710/ here is a code golf for it.
70 Answers
70
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How can I check if multiplying two numbers in Java will cause an overflow?
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14 Answers
14
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How do you get the width and height of a multi-dimensional array?
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answered Nov 23 '10 at 19:52
Reed CopseyReed Copsey
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How do I use the includes method in lodash to check if an object is in the collection?
...s will work because there is only one instance of {"b": 2}:
var a = {"a": 1}, b = {"b": 2};
_.includes([a, b], b);
> true
On the other hand, the where(deprecated in v4) and find methods compare objects by their properties, so they don't require reference equality. As an alternative to includes...
Creating range in JavaScript - strange syntax
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+1000
Understanding this "hack" requires understanding several things:
Why we don't just do Array(5).map(...)
How Function.prototype.ap...
How can I obtain the element-wise logical NOT of a pandas Series?
...: s = pd.Series([True, True, False, True])
In [8]: ~s
Out[8]:
0 False
1 False
2 True
3 False
dtype: bool
Using Python2.7, NumPy 1.8.0, Pandas 0.13.1:
In [119]: s = pd.Series([True, True, False, True]*10000)
In [10]: %timeit np.invert(s)
10000 loops, best of 3: 91.8 µs per loop
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How to pass a single object[] to a params object[]
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100
A simple typecast will ensure the compiler knows what you mean in this case.
Foo((object)new ...