diff --git a/src/lang/en.rs b/src/lang/en.rs index f133ed7..7f6fec4 100644 --- a/src/lang/en.rs +++ b/src/lang/en.rs @@ -1,6 +1,5 @@ use super::{common::StopWordFilter, Language}; use crate::pipeline::{FnWrapper, Pipeline, PipelineFn}; -use regex::Regex; const WORDS: &[&str] = &[ "", "a", "able", "about", "across", "after", "all", "almost", "also", "am", "among", "an", @@ -58,70 +57,8 @@ fn trimmer(token: String) -> Option { ) } -static STEP_2: &[(&str, &str)] = &[ - ("ational", "ate"), - ("tional", "tion"), - ("enci", "ence"), - ("anci", "ance"), - ("izer", "ize"), - ("bli", "ble"), - ("alli", "al"), - ("entli", "ent"), - ("eli", "e"), - ("ousli", "ous"), - ("ization", "ize"), - ("ation", "ate"), - ("ator", "ate"), - ("alism", "al"), - ("iveness", "ive"), - ("fulness", "ful"), - ("ousness", "ous"), - ("aliti", "al"), - ("iviti", "ive"), - ("biliti", "ble"), - ("logi", "log"), -]; - -static STEP_3: &[(&str, &str)] = &[ - ("icate", "ic"), - ("ative", ""), - ("alize", "al"), - ("iciti", "ic"), - ("ical", "ic"), - ("ful", ""), - ("ness", ""), -]; - -// This is a direct port of the stemmer from elasticlunr.js -// It's not very efficient and very not-rusty, but it -// generates identical output. - #[derive(Clone)] -struct Stemmer { - re_mgr0: Regex, - re_mgr1: Regex, - re_meq1: Regex, - re_s_v: Regex, - - re_1a: Regex, - re2_1a: Regex, - re_1b: Regex, - re2_1b: Regex, - re2_1b_2: Regex, - re3_1b_2: Regex, - re4_1b_2: Regex, - - re_1c: Regex, - re_2: Regex, - - re_3: Regex, - - re_4: Regex, - re2_4: Regex, - - re_5: Regex, - re3_5: Regex, -} +struct Stemmer; impl PipelineFn for Stemmer { fn name(&self) -> String { @@ -129,210 +66,538 @@ impl PipelineFn for Stemmer { } fn filter(&self, token: String) -> Option { - Some(self.stem(token)) + self.stem(&token) } } -// vowel -macro_rules! V { - () => { - "[aeiouy]" - }; -} +impl Stemmer { + fn new() -> Self { + Self + } -// consonant sequence -macro_rules! CS { - () => { - "[^aeiou][^aeiouy]*" - }; + fn stem(&self, word: &str) -> Option { + get(word).ok() + } } -// vowel sequence -macro_rules! VS { - () => { - "[aeiouy][aeiou]*" - }; +/// This stemmer implementation is taken directly from rust-stem +/// (https://github.com/minhnhdo/rust-stem) which is licensed under the MIT +/// License as follows: +/// +/// The MIT License (MIT) +/// +/// Copyright (c) 2013 Do Nhat Minh + +/// Member b is a vector of bytes holding a word to be stemmed. +/// The letters are in b[0], b[1] ... ending at b[z->k]. Member k is readjusted +/// downwards as the stemming progresses. Zero termination is not in fact used +/// in the algorithm. +/// +/// Note that only lower case sequences are stemmed. get(...) automatically +/// lowercases the string before processing. +struct PorterStemmer { + b: Vec, + k: usize, + j: usize, } -#[inline] -fn concat_string(strs: &[&str]) -> String { - strs.iter().cloned().collect() -} +impl PorterStemmer { + fn new(word: &str) -> Result { + let b = word.to_ascii_lowercase().into_bytes(); + let k = b.len(); + Ok(PorterStemmer { b: b, k: k, j: 0 }) + } -impl Stemmer { - fn new() -> Self { - let mgr0 = concat!("^(", CS!(), ")?", VS!(), CS!()); - let meq1 = concat!("^(", CS!(), ")?", VS!(), CS!(), "(", VS!(), ")?$"); - let mgr1 = concat!("^(", CS!(), ")?", VS!(), CS!(), VS!(), CS!()); - let s_v = concat!("^(", CS!(), ")?", V!()); - - let re_mgr0 = Regex::new(mgr0).unwrap(); - let re_mgr1 = Regex::new(mgr1).unwrap(); - let re_meq1 = Regex::new(meq1).unwrap(); - let re_s_v = Regex::new(s_v).unwrap(); - - let re_1a = Regex::new("^(.+?)(ss|i)es$").unwrap(); - let re2_1a = Regex::new("^(.+?)([^s])s$").unwrap(); - let re_1b = Regex::new("^(.+?)eed$").unwrap(); - let re2_1b = Regex::new("^(.+?)(ed|ing)$").unwrap(); - let re2_1b_2 = Regex::new("(at|bl|iz)$").unwrap(); - let re3_1b_2 = Regex::new("([^aeiouylsz]{2})$").unwrap(); - let re4_1b_2 = Regex::new(concat!("^", CS!(), V!(), "[^aeiouwxy]$")).unwrap(); - - let re_1c = Regex::new("^(.+?[^aeiou])y$").unwrap(); - let re_2 = Regex::new( - "^(.+?)(ational|tional|enci|anci|izer|bli|alli|entli|eli|ousli|\ - ization|ation|ator|alism|iveness|fulness|ousness|aliti|iviti|biliti|logi)$", - ) - .unwrap(); - - let re_3 = Regex::new("^(.+?)(icate|ative|alize|iciti|ical|ful|ness)$").unwrap(); - - let re_4 = Regex::new( - "^(.+?)(al|ance|ence|er|ic|able|ible|ant|ement|ment|ent|ou|ism|ate|iti|ous|ive|ize)$", - ) - .unwrap(); - let re2_4 = Regex::new("^(.+?)(s|t)(ion)$").unwrap(); - - let re_5 = Regex::new("^(.+?)e$").unwrap(); - let re3_5 = Regex::new(concat!("^", CS!(), V!(), "[^aeiouwxy]$")).unwrap(); - - Stemmer { - re_mgr0, - re_mgr1, - re_meq1, - re_s_v, - re_1a, - re2_1a, - re_1b, - re2_1b, - re2_1b_2, - re3_1b_2, - re4_1b_2, - re_1c, - re_2, - re_3, - re_4, - re2_4, - re_5, - re3_5, + /// stem.is_consonant(i) is true <=> stem[i] is a consonant + #[inline] + fn is_consonant(&self, i: usize) -> bool { + match self.b[i] { + b'a' | b'e' | b'i' | b'o' | b'u' => false, + b'y' => { + if i == 0 { + true + } else { + !self.is_consonant(i - 1) + } + } + _ => true, } } - /// Implements the Porter stemming algorithm - pub fn stem(&self, mut w: String) -> String { - if w.len() < 3 { - return w; + /// stem.measure() measures the number of consonant sequences in [0, j). + /// if c is a consonant sequence and v a vowel sequence, and <..> indicates + /// arbitrary presence, + /// + /// ~~~notrust + /// gives 0 + /// vc gives 1 + /// vcvc gives 2 + /// vcvcvc gives 3 + /// .... + /// ~~~ + fn measure(&self) -> usize { + let mut n = 0; + let mut i = 0; + let j = self.j; + loop { + if i >= j { + return n; + } + if !self.is_consonant(i) { + break; + } + i += 1; } - - let starts_with_y = w.as_bytes()[0] == b'y'; - if starts_with_y { - w.remove(0); - w.insert(0, 'Y'); + i += 1; + loop { + loop { + if i >= j { + return n; + } + if self.is_consonant(i) { + break; + } + i += 1; + } + i += 1; + n += 1; + loop { + if i >= j { + return n; + } + if !self.is_consonant(i) { + break; + } + i += 1; + } + i += 1; } + } - // TODO: There's probably a better way to handle the - // borrowchecker than cloning w a million times + /// stem.has_vowel() is TRUE <=> [0, j-1) contains a vowel + fn has_vowel(&self) -> bool { + for i in 0..self.j { + if !self.is_consonant(i) { + return true; + } + } + false + } - // Step 1a - if let Some(caps) = self.re_1a.captures(&w.clone()) { - w = concat_string(&[&caps[1], &caps[2]]); + /// stem.double_consonant(i) is TRUE <=> i,(i-1) contain a double consonant. + #[inline] + fn double_consonant(&self, i: usize) -> bool { + if i < 1 { + false + } else if self.b[i] != self.b[i - 1] { + false + } else { + self.is_consonant(i) } - if let Some(caps) = self.re2_1a.captures(&w.clone()) { - w = concat_string(&[&caps[1], &caps[2]]); + } + + /// cvc(z, i) is TRUE <=> i-2,i-1,i has the form consonant - vowel - consonant + /// and also if the second c is not w,x or y. this is used when trying to + /// restore an e at the end of a short word. e.g. + /// + /// ~~~notrust + /// cav(e), lov(e), hop(e), crim(e), but + /// snow, box, tray. + /// ~~~ + fn cvc(&self, i: usize) -> bool { + if i < 2 || !self.is_consonant(i) || self.is_consonant(i - 1) || !self.is_consonant(i - 2) { + false + } else { + match self.b[i] { + b'w' | b'x' | b'y' => false, + _ => true, + } } + } - // Step 1b - if let Some(caps) = self.re_1b.captures(&w.clone()) { - let stem = &caps[1]; - if self.re_mgr0.is_match(stem) { - w.pop(); + /// stem.ends(s) is true <=> [0, k) ends with the string s. + fn ends(&mut self, _s: &str) -> bool { + let s = _s.as_bytes(); + let len = s.len(); + if len > self.k { + false + } else { + if &self.b[self.k - len..self.k] == s { + self.j = self.k - len; + true + } else { + false } - } else if let Some(caps) = self.re2_1b.captures(&w.clone()) { - let stem = &caps[1]; - if self.re_s_v.is_match(stem) { - w = stem.into(); + } + } - let mut re3_1b_2_matched = false; + /// stem.setto(s) sets [j,k) to the characters in the string s, + /// readjusting k. + fn set_to(&mut self, s: &str) { + let s = s.as_bytes(); + let len = s.len(); + for i in 0..(len) { + self.b[self.j + i] = s[i]; + } + self.k = self.j + len; + } - if self.re2_1b_2.is_match(&w) { - w.push('e'); - } else if let Some(m) = self.re3_1b_2.find(&w.clone()) { - let mut suffix = m.as_str().chars(); - // Make sure the two characters are the same since we can't use backreferences - if suffix.next() == suffix.next() { - re3_1b_2_matched = true; - w.pop(); - } - } + /// self.replace(s) is used further down. + #[inline] + fn r(&mut self, s: &str) { + if self.measure() > 0 { + self.set_to(s); + } + } - // re4_1b_2 still runs if re3_1b_2 matches but - // the matched chcaracters are not the same - if !re3_1b_2_matched && self.re4_1b_2.is_match(&w) { - w.push('e'); + /// stem.step1ab() gets rid of plurals and -ed or -ing. e.g. + /// + /// ~~~~notrust + /// caresses -> caress + /// ponies -> poni + /// ties -> ti + /// caress -> caress + /// cats -> cat + /// + /// feed -> feed + /// agreed -> agree + /// disabled -> disable + /// + /// matting -> mat + /// mating -> mate + /// meeting -> meet + /// milling -> mill + /// messing -> mess + /// + /// meetings -> meet + /// ~~~~ + fn step1ab(&mut self) { + if self.b[self.k - 1] == b's' { + if self.ends("sses") { + self.k -= 2; + } else if self.ends("ies") { + self.set_to("i"); + } else if self.b[self.k - 2] != b's' { + self.k -= 1; + } + } + if self.ends("eed") { + if self.measure() > 0 { + self.k -= 1 + } + } else if (self.ends("ed") || self.ends("ing")) && self.has_vowel() { + self.k = self.j; + if self.ends("at") { + self.set_to("ate"); + } else if self.ends("bl") { + self.set_to("ble"); + } else if self.ends("iz") { + self.set_to("ize"); + } else if self.double_consonant(self.k - 1) { + self.k -= 1; + match self.b[self.k - 1] { + b'l' | b's' | b'z' => self.k += 1, + _ => (), } + } else if self.measure() == 1 && self.cvc(self.k - 1) { + self.set_to("e"); } } + } - // Step 1c - replace suffix y or Y by i if preceded by a non-vowel which is not the first - // letter of the word (so cry -> cri, by -> by, say -> say) - if let Some(caps) = self.re_1c.captures(&w.clone()) { - let stem = &caps[1]; - w = concat_string(&[stem, "i"]); + /// stem.step1c() turns terminal y to i when there is another vowel in the stem. + fn step1c(&mut self) { + if self.ends("y") && self.is_consonant(self.k - 2) && self.k > 2 { + self.b[self.k - 1] = b'i'; } + } - // Step 2 - if let Some(caps) = self.re_2.captures(&w.clone()) { - let stem = &caps[1]; - let suffix = &caps[2]; - if self.re_mgr0.is_match(stem) { - w = concat_string(&[stem, STEP_2.iter().find(|&&(k, _)| k == suffix).unwrap().1]); + /// stem.step2() maps double suffices to single ones. so -ization ( = -ize + /// plus -ation) maps to -ize etc. note that the string before the suffix + /// must give m(z) > 0. + fn step2(&mut self) { + match self.b[self.k - 2] { + b'a' => { + if self.ends("ational") { + self.r("ate"); + return; + } + if self.ends("tional") { + self.r("tion"); + return; + } + } + b'c' => { + if self.ends("enci") { + self.r("ence"); + return; + } + if self.ends("anci") { + self.r("ance"); + return; + } + } + b'e' => { + if self.ends("izer") { + self.r("ize"); + return; + } + } + b'l' => { + if self.ends("bli") { + self.r("ble"); + return; + } /*-DEPARTURE-*/ + + /* To match the published algorithm, replace this line with + 'l' => { + if self.ends("abli") { self.r("able"); return } */ + + if self.ends("alli") { + self.r("al"); + return; + } + if self.ends("entli") { + self.r("ent"); + return; + } + if self.ends("eli") { + self.r("e"); + return; + } + if self.ends("ousli") { + self.r("ous"); + return; + } } + b'o' => { + if self.ends("ization") { + self.r("ize"); + return; + } + if self.ends("ation") { + self.r("ate"); + return; + } + if self.ends("ator") { + self.r("ate"); + return; + } + } + b's' => { + if self.ends("alism") { + self.r("al"); + return; + } + if self.ends("iveness") { + self.r("ive"); + return; + } + if self.ends("fulness") { + self.r("ful"); + return; + } + if self.ends("ousness") { + self.r("ous"); + return; + } + } + b't' => { + if self.ends("aliti") { + self.r("al"); + return; + } + if self.ends("iviti") { + self.r("ive"); + return; + } + if self.ends("biliti") { + self.r("ble"); + return; + } + } + b'g' => { + if self.ends("logi") { + self.r("log"); + return; + } + } /*-DEPARTURE-*/ + /* To match the published algorithm, delete this line */ + _ => (), } + } - // Step 3 - if let Some(caps) = self.re_3.captures(&w.clone()) { - let stem = &caps[1]; - let suffix = &caps[2]; - if self.re_mgr0.is_match(stem) { - w = concat_string(&[stem, STEP_3.iter().find(|&&(k, _)| k == suffix).unwrap().1]); + /// stem.step3() deals with -ic-, -full, -ness etc. similar strategy to step2. + fn step3(&mut self) { + match self.b[self.k - 1] { + b'e' => { + if self.ends("icate") { + self.r("ic"); + return; + } + if self.ends("ative") { + self.r(""); + return; + } + if self.ends("alize") { + self.r("al"); + return; + } + } + b'i' => { + if self.ends("iciti") { + self.r("ic"); + return; + } + } + b'l' => { + if self.ends("ical") { + self.r("ic"); + return; + } + if self.ends("ful") { + self.r(""); + return; + } + } + b's' => { + if self.ends("ness") { + self.r(""); + return; + } } + _ => (), } + } - // Step 4 - if let Some(caps) = self.re_4.captures(&w.clone()) { - let stem = &caps[1]; - if self.re_mgr1.is_match(stem) { - w = stem.into(); + /// stem.step4() takes off -ant, -ence etc., in context vcvc. + fn step4(&mut self) { + match self.b[self.k - 2] { + b'a' => { + if self.ends("al") { + } else { + return; + } } - } else if let Some(caps) = self.re2_4.captures(&w.clone()) { - let stem = concat_string(&[&caps[1], &caps[2]]); - if self.re_mgr1.is_match(&stem) { - w = stem; + b'c' => { + if self.ends("ance") { + } else if self.ends("ence") { + } else { + return; + } } + b'e' => { + if self.ends("er") { + } else { + return; + } + } + b'i' => { + if self.ends("ic") { + } else { + return; + } + } + b'l' => { + if self.ends("able") { + } else if self.ends("ible") { + } else { + return; + } + } + b'n' => { + if self.ends("ant") { + } else if self.ends("ement") { + } else if self.ends("ment") { + } else if self.ends("ent") { + } else { + return; + } + } + b'o' => { + if self.ends("ion") && (self.b[self.j - 1] == b's' || self.b[self.j - 1] == b't') { + } else if self.ends("ou") { + } else { + return; + } + /* takes care of -ous */ + } + b's' => { + if self.ends("ism") { + } else { + return; + } + } + b't' => { + if self.ends("ate") { + } else if self.ends("iti") { + } else { + return; + } + } + b'u' => { + if self.ends("ous") { + } else { + return; + } + } + b'v' => { + if self.ends("ive") { + } else { + return; + } + } + b'z' => { + if self.ends("ize") { + } else { + return; + } + } + _ => return, + } + if self.measure() > 1 { + self.k = self.j } + } - // Step 5 - if let Some(caps) = self.re_5.captures(&w.clone()) { - let stem = &caps[1]; - if self.re_mgr1.is_match(stem) - || (self.re_meq1.is_match(stem) && !(self.re3_5.is_match(stem))) - { - w = stem.into(); + /// stem.step5() removes a final -e if self.measure() > 0, and changes -ll + /// to -l if self.measure() > 1. + fn step5(&mut self) { + self.j = self.k; + if self.b[self.k - 1] == b'e' { + let a = self.measure(); + if a > 1 || a == 1 && !self.cvc(self.k - 2) { + self.k -= 1 } } - - if w.ends_with("ll") && self.re_mgr1.is_match(&w) { - w.pop(); + if self.b[self.k - 1] == b'l' && self.double_consonant(self.k - 1) && self.measure() > 1 { + self.k -= 1; } + } - // replace the original 'y' - if starts_with_y { - w.remove(0); - w.insert(0, 'y'); - } + #[inline] + fn get(&self) -> String { + String::from_utf8(self.b[..self.k].to_vec()).unwrap() + } +} - w +fn get(word: &str) -> Result { + if word.len() > 2 { + match PorterStemmer::new(word) { + Ok(w) => { + let mut mw = w; + mw.step1ab(); + mw.step1c(); + mw.step2(); + mw.step3(); + mw.step4(); + mw.step5(); + Ok(mw.get()) + } + Err(e) => Err(e), + } + } else { + Ok(word.to_owned()) } } @@ -448,11 +713,13 @@ mod tests { ("knots", "knot"), ("lay", "lay"), ("try", "tri"), + ("by", "by"), ]; let stemmer = Stemmer::new(); for &(input, output) in cases.iter() { - assert_eq!(&stemmer.stem(input.into()), output); + let result = stemmer.stem(input.into()).unwrap(); + assert_eq!(&result, output); } } }