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Why is XOR the default way to combine hashes?
Say you have two hashes H(A) and H(B) and you want to combine them. I've read that a good way to combine two hashes is to XOR them, e.g. XOR( H(A), H(B) ) .
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Converting RGB to grayscale/intensity
When converting from RGB to grayscale, it is said that specific weights to channels R, G, and B ought to be applied. These weights are: 0.2989, 0.5870, 0.1140.
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Reset C int array to zero : the fastest way?
Assuming that we have a T myarray[100] with T = int, unsigned int, long long int or unsigned long long int, what is the fastest way to reset all its content to zero (not only for initialization but to reset the content several times in my program)? Maybe with memset?
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What's the (hidden) cost of Scala's lazy val?
One handy feature of Scala is lazy val , where the evaluation of a val is delayed until it's necessary (at first access).
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Javascript calculate the day of the year (1 - 366)
How do I use javascript to calculate the day of the year, from 1 - 366? For example:
22 Answers
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Replace all 0 values to NA
I have a dataframe with some numeric columns. Some row has a 0 value which should be considered as null in statistical analysis. What is the fastest way to replace all the 0 value to NULL in R?
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Why is a round-trip conversion via a string not safe for a double?
Recently I have had to serialize a double into text, and then get it back. The value seems to not be equivalent:
3 Answers
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All falsey values in JavaScript
What are the values in JavaScript that are 'falsey' , meaning that they evaluate as false in expressions like if(value) , value ? and !value ?
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Is it possible to change only the alpha of a rgba background colour on hover?
I have a set of <a> tags with differing rgba background colours but the same alpha. Is it possible to write a single css style that will change only the opacity of the rgba attribute?
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Undefined method 'task' using Rake 0.9.0
I just updated Rake to the latest version ( 0.9.0.beta.4 ) and the rake command ends up with the following error message:
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