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Representing null in JSON
...
Let's evaluate the parsing of each:
http://jsfiddle.net/brandonscript/Y2dGv/
var json1 = '{}';
var json2 = '{"myCount": null}';
var json3 = '{"myCount": 0}';
var json4 = '{"myString": ""}';
var json5 = '{"myString": "null"}';
var json6 = '{"myArray": []}';
console.log(JSON.parse(js...
Safely override C++ virtual functions
I have a base class with a virtual function and I want to override that function in a derived class. Is there some way to make the compiler check if the function I declared in the derived class actually overrides a function in the base class? I would like to add some macro or something that ensures ...
How to kill a child process after a given timeout in Bash?
... launches a child process that crashes (actually, hangs) from time to time and with no apparent reason (closed source, so there isn't much I can do about it). As a result, I would like to be able to launch this process for a given amount of time, and kill it if it did not return successfully after a...
Why do people write the #!/usr/bin/env python shebang on the first line of a Python script?
...y having a #! at the start of the first line, followed by the interpreter (and any flags it may need).
If you're talking about other platforms, of course, this rule does not apply (but that "shebang line" does no harm, and will help if you ever copy that script to a platform with a Unix base, such ...
Running JAR file on Windows
...amed helloworld.jar .
In order to run it, I'm executing the following command in a command-line window:
25 Answers
...
How to debug an apache virtual host configuration?
...ck configuration files for syntax errors:
# Red Hat-based (Fedora, CentOS) and OSX
httpd -t
# Debian-based (Ubuntu)
apache2ctl -t
# MacOS
apachectl -t
List virtual hosts
To list all virtual hosts, and their locations:
# Red Hat-based (Fedora, CentOS) and OSX
httpd -S
# Debian-based (Ubuntu)
apac...
How to make Git “forget” about a file that was tracked but is now in .gitignore?
...e you need to remove it from the index. This can be achieved with this command.
git rm --cached <file>
If you want to remove a whole folder, you need to remove all files in it recursively.
git rm -r --cached <folder>
The removal of the file from the head revision will happen on the...
What does the exclamation mark do before the function?
...put () at the end: !function foo() {}() which has higher precedence than ! and instantly calls the function.
So what the author is doing is saving a byte per function expression; a more readable way of writing it would be this:
(function(){})();
Lastly, ! makes the expression return true. This i...
How to create a dialog with “yes” and “no” options?
I am going to make a button to take an action and save the data into a database.
13 Answers
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SQL select only rows with max value on a column [duplicate]
...ou join your table to the sub-query with equality on both group-identifier and max-value-in-group:
SELECT a.id, a.rev, a.contents
FROM YourTable a
INNER JOIN (
SELECT id, MAX(rev) rev
FROM YourTable
GROUP BY id
) b ON a.id = b.id AND a.rev = b.rev
Left Joining with self, tweaking join...