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Fast permutation -> number -> permutation mapping algorithms
...you have n possibilities, so you can describe this with a number between 0 and n-1. For the position that the next element ends up at, you have n-1 remaining possibilities, so you can describe this with a number between 0 and n-2.
Et cetera until you have n numbers.
As an example for n = 5, consid...
How do you set, clear, and toggle a single bit?
How do you set, clear, and toggle a bit?
30 Answers
30
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What is the scope of variables in JavaScript?
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TLDR
JavaScript has lexical (also called static) scoping and closures. This means you can tell the scope of an identifier by looking at the source code.
The four scopes are:
Global - visible by everything
Function - visible within a function (and its sub-functions and blocks)
Bloc...
Grep characters before and after match?
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3 characters before and 4 characters after
$> echo "some123_string_and_another" | grep -o -P '.{0,3}string.{0,4}'
23_string_and
share
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im...
CPU Privilege Rings: Why rings 1 and 2 aren't used?
...the modern protection model) only has a concept of privileged (ring 0,1,2) and unprivileged, the benefit to rings 1 and 2 were diminished greatly.
The intent by Intel in having rings 1 and 2 is for the OS to put device drivers at that level, so they are privileged, but somewhat separated from the r...
Why should eval be avoided in Bash, and what should I use instead?
Time and time again, I see Bash answers on Stack Overflow using eval and the answers get bashed, pun intended, for the use of such an "evil" construct. Why is eval so evil?
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How to validate phone numbers using regex
...ogether a comprehensive regex to validate phone numbers. Ideally it would handle international formats, but it must handle US formats, including the following:
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How to pretty-print a numpy.array without scientific notation and with given precision?
...printoptions to set the precision of the output:
import numpy as np
x=np.random.random(10)
print(x)
# [ 0.07837821 0.48002108 0.41274116 0.82993414 0.77610352 0.1023732
# 0.51303098 0.4617183 0.33487207 0.71162095]
np.set_printoptions(precision=3)
print(x)
# [ 0.078 0.48 0.413 0.83 ...
What values should I use for CFBundleVersion and CFBundleShortVersionString?
This is my first iOS app submission and I don't want my app rejected.
7 Answers
7
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Rotating a two-dimensional array in Python
... answered Dec 7 '11 at 19:43
Andrew ClarkAndrew Clark
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