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Why does ~True result in -2?
...00000001
and ~1 is:
11111110
Which is -2 in Two's complement1
1 Flip all the bits, add 1 to the resulting number and interpret the result as a binary representation of the magnitude and add a negative sign (since the number begins with 1):
11111110 → 00000001 → 00000010
↑ ...
How to check if multiple array keys exists
... check (like in the original question), it's probably easy enough to just call array_key_exists() twice to check if the keys exists.
if (array_key_exists("story", $arr) && array_key_exists("message", $arr)) {
// Both keys exist.
}
However this obviously doesn't scale up well to many k...
Difference between Observer, Pub/Sub, and Data Binding
...
Here's my take on the three:
Data Binding
Essentially, at the core this just means "the value of property X on object Y is semantically bound to the value of property A on object B. No assumptions are made as to how Y knows or is fed changes on object B.
Observer, or Obser...
What is the behavior difference between return-path, reply-to and from?
...
Now, let's describe the different "FROM"s.
The return path (sometimes called the reverse path, envelope sender, or envelope from — all of these terms can be used interchangeably) is the value used in the SMTP session in the MAIL FROM command. As you can see, this does not need to be the same v...
how to disable DIV element and everything inside [duplicate]
I need to disable a DIV and all it's content using Javascript. I can swear that doing a simple
5 Answers
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What is the difference between Directory.EnumerateFiles vs Directory.GetFiles?
...many files and directories, EnumerateFiles can be more efficient.
So basically, EnumerateFiles returns an IEnumerable which can be lazily evaluated somewhat, whereas GetFiles returns a string[] which has to be fully populated before it can return.
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What's the fastest way to merge/join data.frames in R?
...(y) from main.d group by g1, g2"))
)
The outputs from the two benchmark call comparing the merge calculations are:
Joining by: x
test replications elapsed relative user.self sys.self user.child sys.child
3 data.table 1 0.34 1.000000 0.31 0.01 NA NA
2 ...
Truncate all tables in a MySQL database in one command?
Is there a query (command) to truncate all the tables in a database in one operation? I want to know if I can do this with one single query.
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How do I view all commits for a specific day?
...:00" --until="2013-11-13 00:00" & would also work if you have gitk installed.
– HelloGoodbye
Mar 4 '16 at 12:50
6
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Which iomanip manipulators are 'sticky'?
... the comments below:
By Martin:
@Chareles: Then by this requirement all manipulators are sticky. Except setw which seems to be reset after use.
By Charles:
Exactly! and the only reason that setw appears to behave differently is because there are requirements on formatted output operat...