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Matching an empty input box using CSS
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If only the field is required you could go with input:valid
#foo-thing:valid + .msg { visibility: visible!important; }
<input type="text" id="foo-thing" required="required">
<span class="msg" style="visibility: hidden;">Yay not empty</span...
Extracting specific columns from a data frame
I have an R data frame with 6 columns, and I want to create a new dataframe that only has three of the columns.
10 Answers
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How can I ignore a property when serializing using the DataContractSerializer?
...'t have to include DataContract / DataMember attributes on the class and it will just serialize the entire thing. This is the behavior I am using, but now I need to ignore one property from the serializer. I know that one way to do this is to add the DataContract attribute to the class, and ju...
How to initialize log4j properly?
...og4j.properties or log4j.xml on the classpath.
You can control which file it uses to initialize itself by setting system properties as described here (Look for the "Default Initialization Procedure" section).
For example:
java -Dlog4j.configuration=customName ....
Will cause log4j to look for ...
font-style: italic vs oblique in CSS
...at has been skewed a certain number of degrees (8-12 degrees, usually). An italic is created by the type designer with specific characters (notably lowercase a) drawn differently to create a more calligraphic, as well as slanted version.
Some type foundries have arbitrarily created obliques that ar...
Set width of TextView in terms of characters
...And the winner is: set the minEms attribute (android:minEms) !!!
So "ems" it turns out refers to the size of the widest character, typically an "M", get it? So setting minEms to an integer value say 3, on an EditText or TextView should ensure it's at least 3 characters wide. You can set the maxEms ...
How to find duplicates in 2 columns not 1
I have a MySQL database table with two columns that interest me. Individually they can each have duplicates, but they should never have a duplicate of BOTH of them having the same value.
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How to handle multiple heterogeneous inputs with Logstash?
...of logs.
In the logstash configuration file, you can specific each input with different type.
Then in the filter you can use if to distinct different processing,
and also at the output you can use "if" output to different destination.
input {
file {
type => "technical"
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What is std::string::c_str() lifetime?
In one of my programs, I have to interface with some legacy code that works with const char* .
7 Answers
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Ruby sleep or delay less than a second?
I'm making a script with ruby that must render frames at 24 frames per second, but I need to wait 1/24th of a second between sending the commands. What is the best way to sleep for less than a second?
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