Accessing Android phone via USB cable

Since Android 3 it is no longer possible to access the phone via USB mount. The reason being that Android puts everything into a single partition. As this single partition is always mounted by Android it is not easy to have two users (Android system and PC user) to write on this single partition. Therefore one needs a separate way to access the whole or parts of the filesystem. One solution is ssh, see ssh and rsync for Android, or MTPFS.

apt-get install mtpfs
mtpfs /mnt/sd              # mount
...                        # use it
fusermount -u /mnt/sd      # umount

See also: MTP – what is it, why use it, and how to set it up, or Geräte mit Android 3.0 oder 4.0 via MTP in Ubuntu Linux einbinden (in German).

Lexware Financial Office Pro 2015 does not work with wine

Today I received a free copy of a student-version of Lexware Financial Office Pro 2015 including a license key. Lexware is a financial accounting software which is easy to use and quite well suited for small German enterprises. I installed wine 1.6.2 on Ubuntu 14.04.2 LTS, which consumed almost half a Gigabyte of hard-disk. Then I tried to install Lexware. This simply didn’t work. Searching in Google and winhq.org delivered similar results. So, in short, if you want or need to install Lexware on Linux, just forget it.

Methods of Proof — Diagonalization

eklausmeier:

Very clear presentation on the uncountability of the real numbers, and the halting problem.

Originally posted on Math ∩ Programming:

A while back we featured a post about why learning mathematics can be hard for programmers, and I claimed a major issue was not understanding the basic methods of proof (the lingua franca between intuition and rigorous mathematics). I boiled these down to the “basic four,” direct implication, contrapositive, contradiction, and induction. But in mathematics there is an ever growing supply of proof methods. There are books written about the “probabilistic method,” and I recently went to a lecture where the “linear algebra method” was displayed. There has been recent talk of a “quantum method” for proving theorems unrelated to quantum mechanics, and many more.

So in continuing our series of methods of proof, we’ll move up to some of the more advanced methods of proof. And in keeping with the spirit of the series, we’ll spend most of our time discussing the structural form of the proofs…

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