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Quick-and-dirty way to ensure only one instance of a shell script is running at a time
What's a quick-and-dirty way to make sure that only one instance of a shell script is running at a given time?
40 Answers
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Why is [1,2] + [3,4] = “1,23,4” in JavaScript?
...d for arrays.
What happens is that Javascript converts arrays into strings and concatenates those.
Update
Since this question and consequently my answer is getting a lot of attention I felt it would be useful and relevant to have an overview about how the + operator behaves in general also.
So, h...
Counting inversions in an array
... find all inversion pairs such that A[i] > A[j] . I'm using merge sort and copying array A to array B and then comparing the two arrays, but I'm having a difficult time seeing how I can use this to find the number of inversions. Any hints or help would be greatly appreciated.
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Difference between `set`, `setq`, and `setf` in Common Lisp?
What is the difference between "set", "setq", and "setf" in Common Lisp?
6 Answers
6
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java.lang.UnsupportedClassVersionError: Bad version number in .class file?
... suggestions on the web indicate that the code was compiled in one version and executed in another version (new on old). However, I only have one version of JRE on my system. If I run the commands:
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How to split a string and assign it to variables
In Python it is possible to split a string and assign it to variables:
9 Answers
9
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Is there a difference between YES/NO,TRUE/FALSE and true/false in objective-c?
Simple question really; is there a difference between these values (and is there a difference between BOOL and bool)? A co-worker mentioned that they evaluate to different things in Objective-C, but when I looked at the typedefs in their respective .h files, YES/TRUE/true were all defined as 1 an...
What is the difference between exit(0) and exit(1) in C?
Can anyone tell me? What is the difference between exit(0) and exit(1) in C language?
11 Answers
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~x + ~y == ~(x + y) is always false?
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Assume for the sake of contradiction that there exists some x and some y (mod 2n) such that
~(x+y) == ~x + ~y
By two's complement*, we know that,
-x == ~x + 1
<==> -1 == ~x + x
Noting this result, we have,
~(x+y) == ~x + ~y
<==> ~(x+y) + (x+y) == ~x + ~y...
Convert light frequency to RGB?
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And the Fourmilab article makes the important point that some colours are not representable in RGB (bright oranges being a good example) because you cannot "make" arbitrary colours of light by adding three primary colours tog...