| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/levenshtein_automata-0.2.1/src/lib.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>lib.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../normalize.css"><link rel="stylesheet" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../ayu.css" disabled><link rel="stylesheet" href="../../dark.css" disabled><link rel="stylesheet" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="../../source-script.js"></script><script defer src="../../source-files.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../levenshtein_automata/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../levenshtein_automata/index.html"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="doccomment">/*! |
| |
| Build a deterministic finite automaton (DFA) that computes |
| the levenshtein distance from a given string. |
| |
| |
| # Example |
| |
| ```rust |
| # extern crate levenshtein_automata; |
| use levenshtein_automata::{LevenshteinAutomatonBuilder, Distance}; |
| # fn main() { |
| |
| // Building this factory is not free. |
| let lev_automaton_builder = LevenshteinAutomatonBuilder::new(2, true); |
| |
| // We can now build an entire dfa. |
| let dfa = lev_automaton_builder.build_dfa("Levenshtein"); |
| |
| let mut state = dfa.initial_state(); |
| for &b in "Levenshtain".as_bytes() { |
| state = dfa.transition(state, b); |
| } |
| |
| assert_eq!(dfa.distance(state), Distance::Exact(1)); |
| # } |
| ``` |
| |
| The implementation is based on the following paper |
| **Fast String Correction with Levenshtein-Automata (2002)** by by Klaus Schulz and Stoyan Mihov. |
| I also tried to explain it in the following [blog post](https://fulmicoton.com/posts/levenshtein/). |
| |
| !*/ |
| |
| </span><span class="attribute">#![cfg_attr(test, feature(test))] |
| |
| #[cfg(test)] |
| </span><span class="kw">extern crate </span>test; |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>bench; |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>tests; |
| |
| <span class="kw">mod </span>alphabet; |
| <span class="kw">mod </span>dfa; |
| <span class="kw">mod </span>index; |
| <span class="kw">mod </span>levenshtein_nfa; |
| <span class="kw">mod </span>parametric_dfa; |
| |
| <span class="kw">pub use </span><span class="self">self</span>::dfa::{DFA, SINK_STATE}; |
| <span class="kw">use </span><span class="self">self</span>::index::Index; |
| <span class="kw">pub use </span><span class="self">self</span>::levenshtein_nfa::Distance; |
| <span class="kw">use </span><span class="self">self</span>::levenshtein_nfa::LevenshteinNFA; |
| <span class="kw">use </span><span class="self">self</span>::parametric_dfa::ParametricDFA; |
| |
| <span class="doccomment">/// Builder for Levenshtein Automata. |
| /// |
| /// It wraps a precomputed datastructure that allows to |
| /// produce small (but not minimal) DFA. |
| </span><span class="kw">pub struct </span>LevenshteinAutomatonBuilder { |
| parametric_dfa: ParametricDFA, |
| } |
| |
| <span class="kw">impl </span>LevenshteinAutomatonBuilder { |
| <span class="doccomment">/// Creates a Levenshtein automaton builder. |
| /// The builder |
| /// |
| /// * `max_distance` - maximum distance considered by the automaton. |
| /// * `transposition_cost_one` - assign a distance of 1 for transposition |
| /// |
| /// Building this automaton builder is computationally intensive. |
| /// While it takes only a few milliseconds for `d=2`, it grows exponentially with |
| /// `d`. It is only reasonable to `d <= 5`. |
| </span><span class="kw">pub fn </span>new(max_distance: u8, transposition_cost_one: bool) -> LevenshteinAutomatonBuilder { |
| <span class="kw">let </span>levenshtein_nfa = LevenshteinNFA::levenshtein(max_distance, transposition_cost_one); |
| <span class="kw">let </span>parametric_dfa = ParametricDFA::from_nfa(<span class="kw-2">&</span>levenshtein_nfa); |
| LevenshteinAutomatonBuilder { |
| parametric_dfa: parametric_dfa, |
| } |
| } |
| |
| <span class="doccomment">/// Builds a Finite Determinstic Automaton to compute |
| /// the levenshtein distance to a fixed given `query`. |
| /// |
| /// There is no guarantee that the resulting DFA is minimal |
| /// but its number of states is guaranteed to be smaller |
| /// than `C * (query.len() + 1)` in which C is a constant that depends |
| /// on the distance as well as whether transposition are supported |
| /// or not. |
| /// |
| /// For instance for `d=2` and with transposition, `C=68`. |
| </span><span class="kw">pub fn </span>build_dfa(<span class="kw-2">&</span><span class="self">self</span>, query: <span class="kw-2">&</span>str) -> DFA { |
| <span class="self">self</span>.parametric_dfa.build_dfa(query, <span class="bool-val">false</span>) |
| } |
| |
| <span class="doccomment">/// Builds a Finite Determinstic Automaton that computes |
| /// the prefix levenshtein distance to a given `query`. |
| /// |
| /// Given a test string, the resulting distance is defined as |
| /// |
| /// ```formula |
| /// min( levenshtein(&test_string[..i], query } for i in 0..test_string.len() ) |
| /// ``` |
| /// |
| /// Which translates as *the minimum distance of the prefixes of `test_strings`*. |
| /// |
| /// See also [.build_dfa(...)](./struct.LevenshteinAutomatonBuilder.html#method.build_dfa). |
| </span><span class="kw">pub fn </span>build_prefix_dfa(<span class="kw-2">&</span><span class="self">self</span>, query: <span class="kw-2">&</span>str) -> DFA { |
| <span class="self">self</span>.parametric_dfa.build_dfa(query, <span class="bool-val">true</span>) |
| } |
| } |
| </code></pre></div> |
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