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What is an idempotent operation?
...g that x in the mathematical definition represents the state of an object, and f is an operation that may mutate that object. For example, consider the Python set and its discard method. The discard method removes an element from a set, and does nothing if the element does not exist. So:
my_set.dis...
Can I set enum start value in Java?
... just labels for integers.
Java enums are implemented more like classes - and they can even have multiple attributes.
public enum Ids {
OPEN(100), CLOSE(200);
private final int id;
Ids(int id) { this.id = id; }
public int getValue() { return id; }
}
The big difference is that th...
Getting the last argument passed to a shell script
...last
This one is also pretty portable (again, should work with bash, ksh and sh) and it doesn't shift the arguments, which could be nice.
It uses the fact that for implicitly loops over the arguments if you don't tell it what to loop over, and the fact that for loop variables aren't scoped: they ...
How can I check if an ip is in a network in Python?
...
This article shows you can do it with socket and struct modules without too much extra effort. I added a little to the article as follows:
import socket,struct
def makeMask(n):
"return a mask of n bits as a long integer"
return (2L<<n-1) - 1
def dotted...
How to get the current user in ASP.NET MVC
...king in a class outside of a form you'll either need to Imports System.Web and further qualify with with HttpContext.Current.User.Identity.Name, or directly qualify using the full syntax: System.Web.HttpContext.Current.User.Identity.Name
– Paul
Sep 10 '14 at 14...
What is sharding and why is it important?
I think I understand sharding to be putting back your sliced up data (the shards) into an easy to deal with aggregate that makes sense in the context. Is this correct?
...
How to extract the hostname portion of a URL in JavaScript
...ibility for window.location.origin is not clear. I've checked it in chrome and it returned http://sub.domain.com:port if the port is anything but 80, and http://sub.domain.com if the port is 80.
Special thanks to @torazaburo for mentioning that to me.
...
MySQL Conditional Insert
... WHERE user = 123
AND item = 456)
In this, dual is a table with one row only (found originally in Oracle, now in mysql too). The logic is that the SELECT statement generates a single row of data with the required values, but only when the v...
How do I write stderr to a file while using “tee” with a pipe?
...
I'm assuming you want to still see STDERR and STDOUT on the terminal. You could go for Josh Kelley's answer, but I find keeping a tail around in the background which outputs your log file very hackish and cludgy. Notice how you need to keep an exra FD and do cleanu...
Can I store the .git folder outside the files I want tracked?
...e git as a backup system. So let's say I have a directory ./backup/myfiles and I want to back that up using git. To keep things clean I don't want to have a .git directory in the myfiles folder, so I thought I could create ./backup/git_repos/myfiles. From looking at the git docs, I've tried doing th...