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Select multiple columns in data.table by their numeric indices
...
For versions of data.table >= 1.9.8, the following all just work:
library(data.table)
dt <- data.table(a = 1, b = 2, c = 3)
# select single column by index
dt[, 2]
# b
# 1: 2
# select multiple columns by index
dt[, 2:3]
# b c
# 1: 2 3
# select single column by na...
How to properly check if std::function is empty in C++11?
...'re not checking for an empty lambda, but whether the std::function has a callable target stored in it. The check is well-defined and works because of std::function::operator bool which allows for implicit conversion to bool in contexts where boolean values are required (such as the conditional expr...
How to Update Multiple Array Elements in mongodb
...At this moment it is not possible to use the positional operator to update all items in an array. See JIRA http://jira.mongodb.org/browse/SERVER-1243
As a work around you can:
Update each item individually
(events.0.handled events.1.handled
...) or...
Read the document, do the edits
manually and ...
Undo a particular commit in Git that's been pushed to remote repos
... And use the -n switch if you want the code back, but not automatically committed in again
– jaygooby
Nov 22 '11 at 12:09
18
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Ruby Regexp group matching, assign variables on 1 line
...u can use String#match which will return a MatchData object, you can then call #captures to return an Array of captures. Something like this:
#!/usr/bin/env ruby
string = "RyanOnRails: This is a test"
one, two, three = string.match(/(^.*)(:)(.*)/i).captures
p one #=> "RyanOnRails"
p two #=...
Preview layout with merge root tag in Intellij IDEA/Android Studio
...some attributes to the root view (in this case RelativeLayout) programmatically, like padding. Of course they're not applied in this helper layout (because you use a completely other view). The only solution was to use the whole custom view in the helper layout.
– Felix Edelman...
How can I count the number of matches for a regex?
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matcher.find() does not find all matches, only the next match.
Solution for Java 9+
long matches = matcher.results().count();
Solution for Java 8 and older
You'll have to do the following. (Starting from Java 9, there is a nicer solution)
int count...
What is the difference between 'log' and 'symlog'?
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I finally found some time to do some experiments in order to understand the difference between them. Here's what I discovered:
log only allows positive values, and lets you choose how to handle negative ones (mask or clip).
syml...
Implement paging (skip / take) functionality with this query
...on it is a bit (little bit) difficult. Here is comparison and examples for all SQL server versions: here
So, this could work in SQL Server 2008:
-- SQL SERVER 2008
DECLARE @Start INT
DECLARE @End INT
SELECT @Start = 10,@End = 20;
;WITH PostCTE AS
( SELECT PostId, MAX (Datemade) as LastDate
...
How to redirect to a dynamic login URL in ASP.NET MVC
...o good reason you shouldn't), something at the end of the day is going to call FormsAuthentication.RedirectToLoginPage() which is going to look at the one configured URL. There's only one login URL, ever, and that's just how they designed it.
My stab at the problem (possibly a Rube Goldberg impleme...