# `Unicode.String.Dfa`
[🔗](https://github.com/elixir-unicode/unicode_string/blob/v2.4.1/lib/unicode/string/dfa.ex#L1)

The break-iteration algorithm described in PRI #555 (L2/26-135), section 9.3.2.

A break type is realised by `use`-ing this module with the name of the data
files to compile in:

    defmodule Unicode.String.Dfa.Grapheme do
      use Unicode.String.Dfa, type: "GraphemeClusterBreak"
    end

The automaton recognises the language between one break and the next: it runs
from the last break, remembering the most recent accepting position, and when
no transition exists it reports that position as the next break. Lookaheads,
which only the line break machine uses, let a state report a position recorded
earlier rather than the last accepting one.

No rule of the annex appears as code here. The rules live in the data files
read by `Unicode.String.Dfa.Builder`, which is what makes adopting a new
Unicode version a data update rather than a re-reading of the rules.

---

*Consult [api-reference.md](api-reference.md) for complete listing*