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Quickly reading very large tables as dataframes
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# sqldf as on SO
f <- file("test.csv")
system.time(SQLf <- sqldf("select * from f", dbname = tempfile(), file.format = list(header = T, row.names = F)))
## user system elapsed
## 10.21 0.47 10.73
ff / ffdf
require(ff)
system.time(FFDF <- read.csv.ffdf(file="test.csv",nro...
What is “rvalue reference for *this”?
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If a class instance is not const, overload resolution will preferentially select the non-const version. If the instance is const, the user can only call the const version. And the this pointer is a const pointer, so the instance cannot be changed.
What "r-value reference for this` does is allow yo...
What are good alternatives to SQL (the language)? [closed]
... way in which you use SQL", because SQL, is not truly relational. Example: SELECT Sum(foo) BAR Blah WHERE 1=0. SQL returns null, 100% relational demands a zero. carfield.com.hk/document/misc/SQL_Problems.pdf
– McKay
Oct 28 '10 at 19:53
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Tree data structure in C#
...T>[] AddChildren(params T[] values)
{
return values.Select(AddChild).ToArray();
}
public bool RemoveChild(TreeNode<T> node)
{
return _children.Remove(node);
}
public void Traverse(Action<T> action)
{
...
How do I remove a project configuration in Visual Studio 2008?
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In the Configuration Manager, select "Edit..." in the "Configuration" column for each project (not via the dropdown named Active solution configuration) that has configurations you want to remove.
In the dialog that pops up, mark each unwanted configurat...
How do I see active SQL Server connections?
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when you have to filter for specific db selecting from sys.sysprocesses is better
– Iman
Dec 2 '13 at 4:29
2
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Custom attributes - Yea or nay?
...t known. For example, if it is some kind of integer id, we can't very well select for every possible case. We are then left to parse the class attribute manually which is definitely workable, but not as clear in the code, and in some cases, could be very slow (if there are a lot of candidate element...
What exactly is nullptr?
...rloading a function for both pointers and integers, and passing nullptr to select the pointer version. Passing NULL or 0 would confusingly select the int version.
A cast of nullptr_t to an integral type needs a reinterpret_cast, and has the same semantics as a cast of (void*)0 to an integral type (...
What's the best way to do a backwards loop in C/C#/C++?
...t, the problem with this approach is that an iterator doesn't allow you to selectively pick out items of the array - consider the situation where you wanted to navigate through a portion of an Array, but not the entire thing...
– jesses.co.tt
Feb 17 '16 at 21:5...
A proper wrapper for console.log with correct line number?
...eNumberFromStack(this.stack)
)
};
args = args.concat([suffix]);
// via @paulirish console wrapper
if (console && console.log) {
if (console.log.apply) { console.log.apply(console, args); } else { console.log(args); } // nicer display i...