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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...
How to represent multiple conditions in a shell if statement?
...n this particular case, the parentheses aren't even needed, because -a actually has higher precedence than -o (unlike && and || in the shell - however, inside bash [[ ... ]] conditionals, && also has higher precedence than || ). If you wanted to avoid -a and -o for maximum robustness...
Creating hard and soft links using PowerShell
... Worked also on a Windows10 system.
– FooF
Feb 21 '19 at 4:09
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How can I implement prepend and append with regular JavaScript?
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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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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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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 ...
Multiline string literal in C#
...nt of a string to form a verbatim string literal:
string query = @"SELECT foo, bar
FROM table
WHERE id = 42";
You also do not have to escape special characters when you use this method, except for double quotes as shown in Jon Skeet's answer.
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How to call a function from a string stored in a variable?
...ble to pass arguments using both of these methods as so
$function_name = 'foobar';
$function_name(arg1, arg2);
call_user_func_array($function_name, array(arg1, arg2));
If the function you are calling belongs to an object you can still use either of these
$object->$function_name(arg1, arg2);...
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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