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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...
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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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]])
...
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
2...
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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OS X10.9 环境下部署 QT5.3.1 常见的编译问题 - 更多技术 - 清泛网 - 专注C/C++及内核技术
OS X10.9 环境下部署 QT5.3.1 常见的编译问题出于本身对UNIX系统的好奇，以及身边一群对 Swift 语言各种推崇的苹果教徒的影响，这几天折腾起 MAC OS X来，体验下这个被无数开发者...
出于本身对UNIX系统的好奇，以及身边一群对 Swift ...
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...
How to group dataframe rows into list in pandas groupby?
...b, dtype: object
In [3]: df1 = df.groupby('a')['b'].apply(list).reset_index(name='new')
df1
Out[3]:
a new
0 A [1, 2]
1 B [5, 5, 4]
2 C [6]
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