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What is the difference between Left, Right, Outer and Inner Joins?
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Simple Example: Lets say you have a Students table, and a Lockers table. In SQL, the first table you specify in a join, Students, is the LEFT table, and the second one, Lockers, is the RIGHT table.
Each student can be assigned to a locker, so there is a LockerNumber column in...
Python: fastest way to create a list of n lists
...None, n)]
It does not have to create a new int object in every iteration and is about 15 % faster on my machine.
Edit: Using NumPy, you can avoid the Python loop using
d = numpy.empty((n, 0)).tolist()
but this is actually 2.5 times slower than the list comprehension.
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How to append rows to an R data frame
...rs of the type you want for each column, insert values into those vectors, and then, at the end, create your data.frame.
Continuing with Julian's f3 (a preallocated data.frame) as the fastest option so far, defined as:
# pre-allocate space
f3 <- function(n){
df <- data.frame(x = numeric(n)...
How do I convert seconds to hours, minutes and seconds?
...his is the best way, IMHO, as you can then use arithmetic on the timedelta and any datetime objects.
– Matthew Schinckel
Apr 22 '09 at 3:13
13
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Generating random integer from a range
I need a function which would generate a random integer in given range (including border values). I don't unreasonable quality/randomness requirements, I have four requirements:
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How does one make random number between range for arc4random_uniform()?
so my goal in this codebit is to randomly roll two dice and as we all know your regular die only has 6 sides so I imported Foundation for access to arc4random_uniform(UInt32). I attempted using the range of (1..7) to avoid randomly getting 0 however that returned an error which I didn't enjoy too mu...
Regular expression to check if password is “8 characters including 1 uppercase letter, 1 special cha
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The regular expression you are after will most likely be huge and a nightmare to maintain especially for people who are not that familiar with regular expressions.
I think it would be easier to break your regex down and do it one bit at a time. It might take a bit more to do, but I am ...
Under what circumstances are linked lists useful?
... with a single CAS (+retries).
In a modern GC-d environment - such as Java and .NET - the ABA problem can easily be avoided.
Just wrap items you add in freshly created nodes and do not reuse those nodes - let the GC do its work.
The page on the ABA problem also provides the implementation of a lock...
PowerShell script to return versions of .NET Framework on a machine?
...swers both return the root number on my system for .NET 3.0 (where the WCF and WPF numbers, which are nested under 3.0, are higher -- I can't explain that), and fail to return anything for 4.0 ...
EDIT: For .Net 4.5 and up, this changed slightly again, so there's now a nice MSDN article here expla...
Way to get number of digits in an int?
...thematically, numbers don't have a length, nor do they have digits. Length and digits are both properties of a physical representation of a number in a specific base, i.e. a String.
A logarithm-based solution does (some of) the same things the String-based one does internally, and probably does so ...