大约有 14,100 项符合查询结果（耗时：0.0201秒） [XML]
Which method performs better: .Any() vs .Count() > 0?
in the System.Linq namespace, we can now extend our IEnumerable's to have the Any() and Count() extension methods .
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What are paramorphisms?
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foldr :: (a -> b -> b) -> b -> [a] -> b
para c n (x : xs) = c x xs (para c n xs)
foldr c n (x : xs) = c x (foldr c n xs)
para c n [] = n
foldr c n [] = n
Some people call paramorphisms "primitive recursion" by contrast with catamorphisms (foldr) being "iter...
Xml Namespace breaking my xpath! [duplicate]
I have the following XML:
5 Answers
5
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How to convert 2D float numpy array to 2D int numpy array?
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Use the astype method.
>>> x = np.array([[1.0, 2.3], [1.3, 2.9]])
>>> x
array([[ 1. , 2.3],
[ 1.3, 2.9]])
>>> x.astype(int)
array([[1, 2],
[1, 2]])
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How does java do modulus calculations with negative numbers?
... get a negative number for negative inputs then you can use this:
int r = x % n;
if (r > 0 && x < 0)
{
r -= n;
}
Likewise if you were using a language that returns a negative number on a negative input and you would prefer positive:
int r = x % n;
if (r < 0)
{
r += n;
}
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What is the difference between Python's list methods append and extend?
What's the difference between the list methods append() and extend() ?
20 Answers
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Installing PG gem on OS X - failure to build native extension
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Same error for me and I didn't experience it until I downloaded OS X 10.9 (Mavericks). Sigh, another OS upgrade headache.
Here's how I fixed it (with homebrew):
Install another build of Xcode Tools (typing brew update in the terminal will prompt you to u...
Why are there two kinds of functions in Elixir?
I'm learning Elixir and wonder why it has two types of function definitions:
8 Answers
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Converting string to numeric [duplicate]
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I suspect you are having a problem with factors. For example,
> x = factor(4:8)
> x
[1] 4 5 6 7 8
Levels: 4 5 6 7 8
> as.numeric(x)
[1] 1 2 3 4 5
> as.numeric(as.character(x))
[1] 4 5 6 7 8
Some comments:
You mention that your vector contains the characters "Do...
Complex numbers usage in python [closed]
...tting deeper into Python data types. I can't understand how to use a complex number. Please give me examples of usage of complex numbers in Python.
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