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What does .SD stand for in data.table in R
.SD looks useful but I do not really know what I am doing with it. What does it stand for? Why is there a preceding period (full stop). What is happening when I use it?
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Get class name of object as string in Swift
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Is this really the case? According to the docs for String for this initializer "an unspecified result is supplied automatically by the Swift standard library" when it doesn't conform to Streamable, or CustomStringConvertible, or Cust...
Is there any overhead to declaring a variable within a loop? (C++)
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Stack space for local variables is usually allocated in function scope. So no stack pointer adjustment happens inside the loop, just assigning 4 to var. Therefore these two snippets have the same overhead.
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find -exec with multiple commands
...e? this is failing: find ./* -exec grep -v 'COLD,' {} \; -exec egrep -i "my_string" {} \;
– rajeev
Jan 22 '13 at 16:08
53
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Error installing mysql2: Failed to build gem native extension
I am having some problems when trying to install mysql2 gem for Rails. When I try to install it by running bundle install or gem install mysql2 it gives me the following error:
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What is the best way to concatenate two vectors?
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AB.reserve( A.size() + B.size() ); // preallocate memory
AB.insert( AB.end(), A.begin(), A.end() );
AB.insert( AB.end(), B.begin(), B.end() );
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ActionController::InvalidAuthenticityToken
...h were page cached. Pages got buffered with a stale authenticity token and all actions using the methods post/put/delete where recognized as forgery attempts. Error (422 Unprocessable Entity) was returned to the user.
The solution for Rails 3:
Add:
skip_before_filter :verify_authenticity_token
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How to draw a line in android
...rself just simple and clean add the line in xml.
<View
android:layout_width="match_parent"
android:layout_height="1dp"
android:background="@android:color/black" />
The example code I provided will generate a line that fills the screen in width and has a height of one dp.
If you have ...
How do you create a Swift Date object?
... dateFromString. If you wanted to return a nil on bad parses, you would ideally use a failible initializer; but you cannot do that now (June 2015), because of a limitation in Swift 1.2, so then you're next best choice is to use a class factory method.
A more elaborate example, which addresses both ...
Why is it important to override GetHashCode when Equals method is overridden?
...ot match, they may never be considered equal (Equals will simply never be called).
The GetHashCode() method should reflect the Equals logic; the rules are:
if two things are equal (Equals(...) == true) then they must return the same value for GetHashCode()
if the GetHashCode() is equal, it is not...