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What's the magic of “-” (a dash) in command-line parameters?
...command, every time you change directory, it stores the directory you came from. If you do cd with the special - "directory name", it uses that remembered directory instead of a real one. You can easily switch between two directories quite quickly by using that.
Other commands may treat - as a diff...
What does the fpermissive flag do?
...
Right from the docs:
-fpermissive
Downgrade some diagnostics about nonconformant code from errors to warnings.
Thus, using -fpermissive will allow some nonconforming code to compile.
Bottom line: don't use it unl...
Better naming in Tuple classes than “Item1”, “Item2”
...t first, int second)>. I had to download the System.ValueTuple package from NuGet to get it to work in Visual Studio 2017.
– Matt Davis
Mar 25 '17 at 23:19
18
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pandas DataFrame: replace nan values with average of columns
... CAUTION: if you want to use this for Machine Learning / Data Science: from a Data Science perspective it is wrong to first replace NA and then split into train and test... You MUST first split into train and test, then replace NA by mean on train and then apply this stateful preprocessing model...
NSString property: copy or retain?
...ht work for your own strings, but you never know about strings you receive from frameworks.
– Nikolai Ruhe
May 27 '10 at 12:18
7
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design a stack such that getMinimum( ) should be O(1)
... has better space in general. We still have the min stack, but we only pop from it when the value we pop from the main stack is equal to the one on the min stack. We only push to the min stack when the value being pushed onto the main stack is less than or equal to the current min value. This allows...
How to maintain a Unique List in Java?
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You can use a Set implementation:
Some info from the JAVADoc:
A collection that contains no duplicate elements. More formally, sets contain no pair of elements e1 and e2 such that e1.equals(e2), and at most one null element. As implied by its name, this interface m...
How to rename a file using Python
...tension'
So, you can take your path and create a Path object out of it:
from pathlib import Path
p = Path(some_path)
Just to provide some information around this object we have now, we can extract things out of it. For example, if for whatever reason we want to rename the file by modifying the ...
Why does Apple recommend to use dispatch_once for implementing the singleton pattern under ARC?
... it's faster. It's also semantically cleaner, because it also protects you from multiple threads doing alloc init of your sharedInstance--if they all try at the same exact time. It won't allow two instances to be created. The entire idea of dispatch_once() is "perform something once and only once", ...
Regex expressions in Java, \\s vs. \\s+
... regular expression quantifiers, and they perform matches like this (taken from the documentation):
Greedy quantifiers
X? X, once or not at all
X* X, zero or more times
X+ X, one or more times
X{n} X, exactly n times
X{n,} X, at least n times
X{n,m} X, at least n but not more than m times
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