Nicolas Seriot (Hacker News, Reddit):

The core Unicode algorithms (normalization, casing, bidi, collation) are deliberately bounded, but UTS #35 transliteration rules, under their natural unbounded semantics, are not. This is a result I haven’t found published before.

These rules ship as locale data in ICU, the Unicode library shipped in operating systems, browsers, runtimes, and databases. Whether a given rule file terminates on a given input is undecidable.

[…]

To prove UTS #35 universality, we compile 2-tag systems (Post, 1943), a model proven universal (Cocke & Minsky, 1964), into transliteration rules.

[…]

Transliteration rules were designed to turn “é” into “e”. Three lines of them can compute the Collatz function.

KT_Music:

Inspired by this, I tried creating an implementation that “solves #Sudoku” using only UTS#35 transformation rules 😎

Previously:

• Outlandish SQLite Recursive Query Examples
• Solving the “Miracle Sudoku” in Prolog
• Sudoku Solver

Nicolas Seriot (Hacker News):

Engineering folklore holds that Jira (Atlassian’s project-tracking tool) is Turing-complete. Existing claims point vaguely at automation features without exhibiting a reduction. This article supplies a proof, with setup instructions and execution trace.

[…]

Minsky proved this model Turing-complete (1967). Exhibiting it in Jira’s automation language therefore establishes the reduction. Here is how the model maps onto Jira:

Minsky Machine	Jira
Register A	Count of linked issues of type Bug
Register B	Count of linked issues of type Task
Program Counter	Status of a single Epic issue
Dispatch Table	Jira Automation rules, one per instruction state
Clock	Automation-triggered transitions, or external re-triggering past chain caps