The smartphone world is relatively new, so I suspect there are amazing (yet sometimes unknown) apps that can help various aspects of our lives. I cannot think of a better discussion place for this topic. So,
Which app help you optimize life?
Is there an app you keep searching for in vain? (though it might exist!)
For me (I was searching for both apps for months!! until they were finally created):
Anki, A flashcard memorization app with many useful features.
[From the link] Anki is a program which makes remembering things easy. Because it is a lot more efficient than traditional study methods, you can either greatly decrease your time spent studying, or greatly
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There are several complications addressed in the article, which I did not describe. Anyway, using a "control vector" is considered trivial, and I believe they checked this.