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What does .SD stand for in data.table in R
...ollapse="_")], by=y]
# y V1
# 1: 1 a1_b3_c5
# 2: 3 a2_b4_c6
Basically, the by=y statement breaks the original data.table into these two sub-data.tables
DT[ , print(.SD), by=y]
# <1st sub-data.table, called '.SD' while it's being operated on>
# x v
# 1: a 1
# 2: b 3
# 3: c 5
# &l...
Get JSF managed bean by name in any Servlet related class
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@Tiny: it's in turn called by a JSF artifact within the same thread.
– BalusC
Jul 10 '15 at 4:55
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Symbolic links and synced folders in Vagrant
... that appears to be wrong with their default value for rsync__args (specifically, that one of the default args, --copy-links, seems to be breaking another, --archive, at least as far as copying broken symlinks is concerned).
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SQL Query to concatenate column values from multiple rows in Oracle
...t (with tag E)
extract the text of this
aggregate the xml (concatenate it)
call the resulting column "Result"
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Split a module across several files
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Finally, the Rust compiler also looks in sub-directories for you automatically. For example, the above code will work unchanged with this directory structure:
src/
lib.rs
vector/
mod.rs
vector_b.rs
main.rs
The commands to compile and run remain the same as well.
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Difference between std::system_clock and std::steady_clock?
...2 denote clock types. t1 and t2 are values returned by C1::now() where the call returning t1 happens before the call returning t2 and both of these calls occur before C1::time_point::max(). [ Note: this means C1 did not wrap around between t1 and t2. —end note ]
Expression: C1::is_steady
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JavaScript checking for null vs. undefined and difference between == and ===
...he value of function arguments that weren't provided when the function was called, and as the value you get when you ask an object for a property it doesn't have. But it can also be explicitly used in all of those situations. (There's a difference between an object not having a property, and having ...
What is the AppDelegate for and how do I know when to use it?
...s an excellent answer. I was looking at some sample code that had subviews call the appDelegate do to instruct a view controller to switch to a different subview, and that felt like a code smell. Good to know my nose still works.
– Alan
Dec 20 '11 at 0:06
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Clear back stack using fragments
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This DOES NOT work properly - it will trigger a call to onStart of every fragment in between
– James
Mar 11 '15 at 13:29
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kernel stack and user space stack
...erent CPU architectures implement this in different ways; x86 CPUs automatically switch stackpointers when privilege mode switches occur, and the values to be used for different privilege levels are configurable - by privileged code (i.e. only the kernel).
If a local variable is declared in a...