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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...
What's the safest way to iterate through the keys of a Perl hash?
...h of (key, value) pairs, what is the preferred method of iterating through all the keys? I have heard that using each may in some way have unintended side effects. So, is that true, and is one of the two following methods best, or is there a better way?
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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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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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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
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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 do I disable the security certificate check in Python requests
...erification happens only once per connection so we need to close
# all the opened adapters once we're done. Otherwise, the effects of
# verify=False persist beyond the end of this context manager.
opened_adapters.add(self.get_adapter(url))
settings = old_merge_enviro...
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
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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?
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Creating hard and soft links using PowerShell
... Worked also on a Windows10 system.
– FooF
Feb 21 '19 at 4:09
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