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How do I tar a directory of files and folders without including the directory itself?
...he job in one line. It works well for hidden files as well. "*" doesn't expand hidden files by path name expansion at least in bash. Below is my experiment:
$ mkdir my_directory
$ touch my_directory/file1
$ touch my_directory/file2
$ touch my_directory/.hiddenfile1
$ touch my_directory/.hiddenfile2...
Why is pow(a, d, n) so much faster than a**d % n?
I was trying to implement a Miller-Rabin primality test , and was puzzled why it was taking so long (> 20 seconds) for midsize numbers (~7 digits). I eventually found the following line of code to be the source of the problem:
...
Performance difference for control structures 'for' and 'foreach' in C#
...corlib]System.IDisposable::Dispose()
IL_002f: endfinally
} // end handler
IL_0030: ret
} // end of method Test::IterateOverList
The compiler treats arrays differently, converting a foreach loop basically to a for loop, but not List<T>. Here's the equivalent code for an array:
sta...
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 ...
What is the difference between CHARACTER VARYING and VARCHAR in PostgreSQL?
...rchar, so no difference, see documentation :)
The notations varchar(n) and char(n)
are aliases for character varying(n)
and character(n), respectively.
character without length specifier is
equivalent to character(1). If
character varying is used without
length specifier, the type ac...
What is Compass, what is sass…how do they differ?
I would like to start using compass and sass to speed up development. At the moment, I have installed Sass on a mac and instructed it to watch scss file for input, and a css file for generated output.
...
Python if-else short-hand [duplicate]
...
The most readable way is
x = 10 if a > b else 11
but you can use and and or, too:
x = a > b and 10 or 11
The "Zen of Python" says that "readability counts", though, so go for the first way.
Also, the and-or trick will fail if you put a variable instead of 10 and it evaluates to Fals...
How to set xlim and ylim for a subplot in matplotlib [duplicate]
I would like to limit the X and Y axis in matplotlib but for a speific subplot. As I can see
subplot figure itself doesn't have any axis property. I want for example to change only the limits for the second plot!
...
mongodb, replicates and error: { “$err” : “not master and slaveOk=f...
mongodb, replicates and error: { “$err” : “not master and slaveOk=false”, “code” : 13435出现这个错误的原因是在从库上执行命令导致，默认情况下只有主库可以执行命令。当然可以通过设置使得从库也能执行命令，具体参见：http: s 出现...
Sell me on const correctness
... be changed,
It protects you from making accidental variable assignments, and
The compiler can optimize it. For instance, you are protected from
if( x = y ) // whoops, meant if( x == y )
At the same time, the compiler can generate more efficient code because it knows exactly what the state of...