Unicode's Transliteration Rules Are Turing-Complete
22 points by mpweiher
22 points by mpweiher
Fun fact that not many people seem aware of: APFS is unicode normalization insensitive (NFD or something I think?). e.g. groß and gross will be the same file :D
Another fun fact many people don't seem aware of: Turing completeness is trivial and it sometimes takes effort to avoid (and it should be avoided in cases like this)
Yeah, I know of only one iterated string rewriting system that avoids being Turing complete without an artificial run time limit: previously
It does at times feel like step 1 of not creating something that is accidentally Turing complete is to avoid creating any kind of file format :D
AFAIK Unicode NFC / NFD etc are unrelated to these transliteration rules. It’s unclear to me what these transliterations are for: something like squashing greek or cyrillic to latin? but in what context are these transliterations invoked?
And APFS inherited its case-insensitive normalization from HFS+, it’s a very longstanding weirdness of Mac OS X and its precursors. Tho it’s only in recent months that I have seen people joking about the secret ßh command…
What do you mean by “weirdness” here? Most users don’t expect different capitalization to be different file names, because why would they be? It also creates the hazard of accidentally editing the wrong version of a document, etc.
Case sensitivity is not a particularly user friendly model for file names, outside of developers where it’s useful for the purpose of insuring your build works on case sensitive file systems :D :D