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Elegant way to invert a map in Scala
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Mathematically, the mapping might not be invertible (injective), e.g., from Map[A,B], you can't get Map[B,A], but rather you get Map[B,Set[A]], because there might be different keys associated with same values. So, if you are interested in knowing all the keys, here's the code:
scala> val m...
What is a “Bitmap heap scan” in a query plan?
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The best explanation comes from Tom Lane, which is the algorithm's author unless I'm mistaking. See also the wikipedia article.
In short, it's a bit like a seq scan. The difference is that, rather than visiting every disk page, a bitmap index scan AND...
Valid values for android:fontFamily and what they map to?
...ndroid:fontFamily and 12 variants (see below). Where do these values come from? The documentation for android:fontFamily does not list this information in any place (I checked here , and here ). The strings are listed in the Android styles.xml file in various places, but how do these map back...
Long-held, incorrect programming assumptions [closed]
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That I should have only one exit point from a function/method.
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answered May 20 '09 at 17:17
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Programmatically change log level in Log4j2
...ersion 2.4 FAQ
You can set a logger’s level with the class Configurator from Log4j Core. BUT be aware that the Configurator class is not part of the public API.
// org.apache.logging.log4j.core.config.Configurator;
Configurator.setLevel("com.example.Foo", Level.DEBUG);
// You can also set the r...
Difference between map, applymap and apply methods in Pandas
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Straight from Wes McKinney's Python for Data Analysis book, pg. 132 (I highly recommended this book):
Another frequent operation is applying a function on 1D arrays to each column or row. DataFrame’s apply method does exactly th...
Unable to verify leaf signature
...he necessary certificates to the chain. First install ssl-root-cas package from npm:
npm install ssl-root-cas
This package contains many intermediary certificates that browsers trust but node doesn't.
var sslRootCAs = require('ssl-root-cas/latest')
sslRootCAs.inject()
Will add the missing cert...
Using an HTML button to call a JavaScript function
...mous functions and both must be declared after the element has been parsed from the document. The first method isn't valid XHTML because the onclick attribute isn't in the XHTML specification.
The 1st and 2nd methods are mutually exclusive, meaning using one (the 2nd) will override the other (the ...
Remove menu and status bars in TinyMCE 4
I am trying to remove the menu and status bars from TinyMCE 4 because I want to setup a very basic editor. Is this possible?
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Private vs Protected - Visibility Good-Practice Concern [closed]
...e inheritable, then carefully choose what may be overridden and accessible from subclasses, and make that protected (and final, talking of Java, if you want to make it accessible but not overridable). But be aware that, as soon as you accept to have subclasses of your class, and there is a protected...