pvitz · HackerLangs

vor 13 Tagendiscuss

If it were "the EU", it would be on https://code.europa.eu

letzten Monatdiscuss

You will possibly like Needham's "Visual Differential Geometry and Forms" and even if you don't have much time to study it, it's quite beautiful to look at from time to time.

pvitz

vor 2 Monatendiscuss

Segfault provides something similar with a direct ssh connection: https://www.thc.org/segfault/

pvitz

vor 5 Monatendiscuss

The book "Robot Builder's Bonanza" is a nice introduction and gets you started on the hardware side.

pvitz

vor 7 Monatendiscuss

From the manual:

   The control variable in for loops is read only. If you need to change it, declare a local variable with the same name in the loop body.

Also [0]: Roberto Ierusalimschy > So what's the rationale to make them constant now? Does it have performance > reasons?

Yes. The old code does an implicit "local x = x" for all loops, in case you modify 'x'. With the new semantics, the code only does it when you ask for it.

[0] https://groups.google.com/g/lua-l/c/SlAG5QfpTac

pvitz

vor 7 Monatendiscuss

That symmetries imply conservation laws is pretty fascinating (see the Noether theorem). I guess it seems only strange it you assume already that the conservation law holds.

pvitz

vor 7 Monatendiscuss

When I was a student of physics and came across this paragraph in Feynman's book, I was curious if he really meant the simple technique explained in the article, a more general one (also described in the article with the integral bounds as functions of a parameter) or something else. I don't know, but this led me to read the text "Advanced Calculus" by Edwin Bidwell Wilson (1912), which includes a lot of examples and gems. If there is some young student out there who wants to go well beyond the basic techniques of calculus taught in analysis or mathematical physics courses, have a look at [0].

[0] https://archive.org/details/advancedcalculus031579mbp/mode/1...

pvitz

vor 9 Monatendiscuss

I understood "binaries" in "compressed binaries" as "executables", e.g. like a packed executable, but I see that you mean indeed a binary file (and not e.g. a text file).

pvitz

vor 9 Monatendiscuss

Thanks for your reply and advice! I guess what you describe as "impossible" is the case I am mostly interested in, though more for non-executable binary data. If I am not mistaken, this goes under the term "file fragment classification", but I have been wondering if practitioners might have figured out some better ways than what one can find in scholarly articles.

And yes, searching for the reimplementation beforehand would have saved me some hours :D

pvitz

vor 9 Monatendiscuss

A shot in the dark, but maybe you could give me a hint. Recently, I was interested in extracting sprites from an old game. I was able to reverse the file format of the data archive, which contained the game assets as files. However, I got stuck because the image files were obviously compressed. By chance, I found an open source reimplementation of the game and realised it was LZ77+Huffman compressed, but how would one detect the type of compression and parameters with only the file? That seems a pretty hard problem or are there good heuristics to detect that?

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