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Mapping two integers to one, in a unique and deterministic way
...led pairing functions. Wikipedia introduces a specific pairing function, namely the Cantor pairing function:
Three remarks:
As others have made clear, if you plan to implement a pairing function, you may soon find you need arbitrarily large integers (bignums).
If you don't want to make a distin...
How to render a PDF file in Android
...close();
For more information see the sample app.
For older APIs I recommend Android PdfViewer library, it is very fast and easy to use, licensed under Apache License 2.0:
pdfView.fromAsset(String)
.pages(0, 2, 1, 3, 3, 3) // all pages are displayed by default
.enableSwipe(true)
.swipeHori...
When should I use perror(“…”) and fprintf(stderr, “…”)?
Reading the man pages and some code did not really help me in
understanding the difference between - or better, when I should use - perror("...") or fprintf(stderr, "...") .
...
How do I keep track of pip-installed packages in an Anaconda (Conda) environment?
... Python distribution, and I have started using the Anaconda (Conda) environment. I can use the standard conda install... command to put packages from the distribution into my environments, but to use anything outside (i.e. Flask-WTF, flask-sqlalchemy, and alembic) I need to use pip install in th...
Automatic post-registration user authentication
...ould be automatically logged in with those credentials, instead of being immediately forced to provide their credentials again.
...
json_encode sparse PHP array as JSON array, not JSON object
...uential - it has keys 0 and 2, but doesn't have 1 as a key.
Just having numeric indexes isn't enough. json_encode will only encode your PHP array as a JSON array if your PHP array is sequential - that is, if its keys are 0, 1, 2, 3, ...
You can reindex your array sequentially using the array_value...
Why is git push gerrit HEAD:refs/for/master used instead of git push origin master
...
The documentation for Gerrit, in particular the "Push changes" section, explains that you push to the "magical refs/for/'branch' ref using any Git client tool".
The following image is taken from the Intro to Gerrit. When you push to...
Python function global variables?
...
If you want to simply access a global variable you just use its name. However to change its value you need to use the global keyword.
E.g.
global someVar
someVar = 55
This would change the value of the global variable to 55. Otherwise it would just assign 55 to a local variable.
The or...
How to center the content inside a linear layout?
...
android:gravity handles the alignment of its children,
android:layout_gravity handles the alignment of itself.
So use one of these.
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/too...
Why does this loop produce “warning: iteration 3u invokes undefined behavior” and output more than 4
... strictly speaking, there is no such thing as "unsigned integer overflow") means undefined behaviour. And this means anything can happen, and discussing why does it happen under the rules of C++ doesn't make sense.
C++11 draft N3337: §5.4:1
If during the evaluation of an expression, the result...