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Difference between == and ===
In swift there seem to be two equality operators: the double equals ( == ) and the triple equals ( === ), what is the difference between the two?
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When is memoization automatic in GHC Haskell?
... in foldl' (+) 0 (y ++ [x])
GHC might notice that y does not depend on x and rewrite the function to
f = let y = [1..30000000] in \x -> foldl' (+) 0 (y ++ [x])
In this case, the new version is much less efficient because it will have to read about 1 GB from memory where y is stored, while th...
Which is the fastest algorithm to find prime numbers?
...ly I don't think primegen is the fastest, or even the second-fastest; yafu and primesieve are both faster in general, I think, and certainly over 2^32. Both are (modified) sieves of Eratosthenes rather than the Atkin-Bernstein sieve.
– Charles
Aug 19 '11 at 4:...
Finding quaternion representing the rotation from one vector to another
I have two vectors u and v. Is there a way of finding a quaternion representing the rotation from u to v?
7 Answers
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Getting output of system() calls in Ruby
If I call a command using Kernel#system in Ruby, how do I get its output?
15 Answers
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Explain how finding cycle start node in cycle linked list work?
I understand that Tortoise and Hare's meeting concludes the existence of loop, but how does moving tortoise to beginning of linked list while keeping the hare at meeting place, followed by moving both one step at a time make them meet at starting point of cycle?
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Linear Regression and group by in R
...ction. My data is an annual time series with one field for year (22 years) and another for state (50 states). I want to fit a regression for each state so that at the end I have a vector of lm responses. I can imagine doing for loop for each state then doing the regression inside the loop and adding...
How to detect if a script is being sourced
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This seems to be portable between Bash and Korn:
[[ $_ != $0 ]] && echo "Script is being sourced" || echo "Script is a subshell"
A line similar to this or an assignment like pathname="$_" (with a later test and action) must be on the first line of the s...
Java's L number (long) specification
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There are specific suffixes for long (e.g. 39832L), float (e.g. 2.4f) and double (e.g. -7.832d).
If there is no suffix, and it is an integral type (e.g. 5623), it is assumed to be an int. If it is not an integral type (e.g. 3.14159), it is assumed to be a double.
In all other cases (byte, sho...
Waiting until two async blocks are executed before starting another block
When using GCD, we want to wait until two async blocks are executed and done before moving on to the next steps of execution. What is the best way to do that?
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