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What does !! mean in ruby?
...:
!!nil #=> false
!!"abc" #=> true
!!false #=> false
It's usually not necessary to use though since the only false values to Ruby are nil and false, so it's usually best to let that convention stand.
Think of it as
!(!some_val)
One thing that is it used for legitimately is preventi...
Separation of JUnit classes into special test package?
...they test, but in a different physical directory, like:
myproject/src/com/foo/Bar.java
myproject/test/com/foo/BarTest.java
In a Maven project it would look like this:
myproject/src/main/java/com/foo/Bar.java
myproject/src/test/java/com/foo/BarTest.java
The main point in this is that my test cl...
How to hash a string into 8 digits?
... invocations. See here:
$ python -V
Python 2.7.5
$ python -c 'print(hash("foo"))'
-4177197833195190597
$ python -c 'print(hash("foo"))'
-4177197833195190597
$ python3 -V
Python 3.4.2
$ python3 -c 'print(hash("foo"))'
5790391865899772265
$ python3 -c 'print(hash("foo"))'
-8152690834165248934
This...
JavaScript variables declare outside or inside loop?
In AS3 I believe you should initialise all variables outside loops for increased performance. Is this the case with JavaScript as well? Which is better / faster / best-practice?
...
How can I implement prepend and append with regular JavaScript?
...
so prepend is basically this then function prepend(tag, ele) { var x =document.getElementsByTagName(tag)[0]; x.insertBefore(ele ,x.children[0]); }
– Muhammad Umer
Jul 8 '15 at 19:13
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Big O, how do you calculate/approximate it?
..., but be warned that this topic takes my students a couple of months to finally grasp. You can find more information on the Chapter 2 of the Data Structures and Algorithms in Java book.
There is no mechanical procedure that can be used to get the BigOh.
As a "cookbook", to obtain the BigOh from ...
How to add elements to an empty array in PHP?
...ration, but it also doesn't impose the performance overhead of a function call, which array_push() would. Edit: But, great answer. Effectively the same, and majority of uses won't even notice a performance difference, but helps to know those nuances.
– Mattygabe
...
Disabling implicit animations in -[CALayer setNeedsDisplayInRect:]
...like you can specify any key you could use in setValue:forKey: method, actually specifying complex key paths like bounds.size.
– pqnet
Apr 8 '12 at 17:41
13
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Escape a dollar sign in string interpolation
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Just double it
scala> val name = "foo"
name: String = foo
scala> s"my.package.$name$$"
res0: String = my.package.foo$
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What's to stop malicious code from spoofing the “Origin” header to exploit CORS?
...header Origin: http://foo.com , and bar must respond with Access-Control-Allow-Origin: http://foo.com .
3 Answers
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