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Use of 'prototype' vs. 'this' in JavaScript?
...
The examples have very different outcomes.
Before looking at the differences, the following should be noted:
A constructor's prototype provides a way to share methods and values among instances via the instance's private [[Prot...
Normalize data in pandas
...0.932785 4.535396 0.598124
In [93]: df_norm = (df - df.mean()) / (df.max() - df.min())
In [94]: df_norm
Out[94]:
a b c d
A 0.085789 -0.394348 0.337016 -0.109935
B -0.463830 0.164926 -0.650963 0.256714
C -0.158129 0.605652 -0.035090 -0.573389
D 0.536170 -0...
What part of Hindley-Milner do you not understand?
...orizontal bar means that "[above] implies [below]".
If there are multiple expressions in [above], then consider them anded together; all of the [above] must be true in order to guarantee the [below].
: means has type
∈ means is in. (Likewise ∉ means "is not in".)
Γ is usually used to refer to a...
MySQL Conditional Insert
... DBMS does not impose limitations on which table you select from when you execute an insert, try:
INSERT INTO x_table(instance, user, item)
SELECT 919191, 123, 456
FROM dual
WHERE NOT EXISTS (SELECT * FROM x_table
WHERE user = 123
...
Convert Dictionary to semicolon separated string in c#
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using System.Linq;
string s = string.Join(";", myDict.Select(x => x.Key + "=" + x.Value).ToArray());
(And if you're using .NET 4, or newer, then you can omit the final ToArray call.)
share
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STL 算法 - C/C++ - 清泛网 - 专注C/C++及内核技术
...mplate<class InIt1, class InIt2> bool equal(InIt1 first, InIt1 last, InIt2 x);
template<class InIt1, class InIt2, class Pred> bool equal(InIt1 first, InIt1 last, InIt2 x, Pred pr);
includes
<algorithm>
判断第一个指定范围内的所有元素是否都被第二个范围包含...
What's the difference between a proxy server and a reverse proxy server? [closed]
What is the difference between a proxy server and a reverse proxy server?
21 Answers
2...
How to apply a function to two columns of Pandas dataframe
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Here's an example using apply on the dataframe, which I am calling with axis = 1.
Note the difference is that instead of trying to pass two values to the function f, rewrite the function to accept a pandas Series object, and then inde...
numpy: most efficient frequency counts for unique values in an array
....org/doc/numpy/reference/generated/numpy.bincount.html
import numpy as np
x = np.array([1,1,1,2,2,2,5,25,1,1])
y = np.bincount(x)
ii = np.nonzero(y)[0]
And then:
zip(ii,y[ii])
# [(1, 5), (2, 3), (5, 1), (25, 1)]
or:
np.vstack((ii,y[ii])).T
# array([[ 1, 5],
[ 2, 3],
[ 5, ...