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/*! This crate provides a library for generating efficient regular expressions programmatically that can represent a simple, non-recursive grammar. It uses the [`regex`](https://crates.io/crates/regex) crate for its parsing engine. # Usage This crate is [on crates.io](https://crates.io/crates/pidgin) and can be used by adding `pidgin` to your dependencies in your project's `Cargo.toml`. ```toml [dependencies] pidgin = "0.1.4" ``` and this to your crate root: ```rust extern crate pidgin; ``` # Example: find a date This is like the `regex` example, but considerably more expressive, and once you've matched a date with a `Pidgin` matcher it is easier to determine *how* you matched it and thus convert the match into useful semantics. ```rust use pidgin::Pidgin; use std::error::Error; fn experiment() -> Result<(), Box<Error>> { // set up the initial building for our pidgin grammar let mut p = Pidgin::new() .enclosed(true) .word_bound() .case_insensitive(true); // you can build word lists and add them in let weekdays = vec![ "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday", ]; p.add(&weekdays); // various abbreviations for s in weekdays { p.add_str(&s[0..3]); p.add_str(&s[0..2]); } let g = p.compile(); p.rule("weekday", &g); // for these ones we care about case p = p.case_insensitive(false); // you can build and compile all in one go let g = p.grammar(&vec!["M", "T", "W", "R", "F", "S", "U"]); // add a case to an existing rule p.rule("weekday", &g); // back to case insensitivity p = p.case_insensitive(true); // we can add words to a rule piecemeal let months = vec![ "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December", ]; p.add(&months); for m in months { p.add_str(&m[0..3]); } let g = p.compile(); p.rule("month", &g); for i in 1..31 { p.add_str(i.to_string().as_str()); } let g = p.compile(); p.rule("monthday", &g); for i in 1..31 { p.add_str(i.to_string().as_str()); // allow both 1 and 01, etc. // adding a word such as "10" twice has no ill effect p.add_str(&format!("{:02}", i)); } let g = p.compile(); p.rule("numeric_days", &g); for i in 1..12 { p.add_str(i.to_string().as_str()); p.add_str(&format!("{:02}", i)); } let g = p.compile(); p.rule("numeric_months", &g); // sometimes you may need to add in a handwritten regex // take care with named groups -- names cannot be repeated p.foreign_rule("year", "[12][0-9]{3}|[0-9]{2}")?; // for the following patterns make whitespace optional p = p.normalize_whitespace(false); let g = p.grammar(&vec![ "year / numeric_months / numeric_days", "numeric_months / numeric_days / year", "numeric_days / numeric_months / year", "year - numeric_months - numeric_days", "numeric_months - numeric_days - year", "numeric_days - numeric_months - year", ]); p.rule("numeric_date", &g); // for the remaining rules, whitespace is required if present p = p.normalize_whitespace(true); // and finally, the pattern we've been working towards let date = p.grammar(&vec![ "weekday, month monthday, year", "month monthday", "weekday", "monthday month year", "month monthday, year", "numeric_date", ]); // now test it let matcher = date.matcher()?; // we let whitespace vary assert!(matcher.is_match(" June 6, 1969 ")); // we made it case-insensitive assert!(matcher.is_match("june 6, 1969")); // but we want to respect word boundaries assert!(!matcher.is_match("jejune 6, 1969")); // we can inspect the parse tree let m = matcher.parse("2018/10/6").unwrap(); assert!(m.name("numeric_date").is_some()); assert_eq!(m.name("year").unwrap().as_str(), "2018"); let m = matcher.parse("Friday").unwrap(); assert!(!m.name("numeric_date").is_some()); assert!(m.name("weekday").is_some()); // still more crazy things we allow assert!(matcher.is_match("F")); assert!(matcher.is_match("friday")); assert!(matcher.is_match("Fri")); // but we said single-letter days had to be capitalized assert!(!matcher.is_match("f")); println!("{}", date); Ok(()) } ``` The `println!` in the example above will produces a BNF-esque description of the grammar. ```bash TOP := (?i) \b{monthday}(?-i:\s+){month}(?-i:\s+){year}|{month}(?-i:\s+){monthday}(:?,(?-i:\s+){year})?|{weekday}(:?,(?-i:\s+){month}(?-i:\s+){monthday},(?-i:\s+){year})?|{numeric_date}\b monthday := (?i) \b[4-9]|30?|1[0-9]?|2[0-9]?\b month := (?i) \bMa(?:y|r(:?ch)?)|Oct(:?ober)?|Dec(:?ember)?|Feb(:?ruary)?|Nov(:?ember)?|Sep(:?tember)?|A(?:pr(:?il)?|ug(:?ust)?)|J(?:u(?:ly?|ne?)|an(:?uary)?)\b year := [12][0-9]{3}|[0-9]{2} weekday := (?i) (?:\b(?:Fr(:?i(:?day)?)?|Mo(:?n(:?day)?)?|We(:?d(:?nesday)?)?|S(?:u(:?n(:?day)?)?|a(:?t(:?urday)?)?)|T(?:u(:?e(:?sday)?)?|h(:?u(:?rsday)?)?))\b)|(?-i:\b[FMR-UW]\b) numeric_date := (?i) \b{year}(?-i:\s*)(?:\-(?-i:\s*){numeric_months}(?-i:\s*)\-|/(?-i:\s*){numeric_months}(?-i:\s*)/)(?-i:\s*){numeric_days}|{numeric_days}(?-i:\s*)(?:\-(?-i:\s*){numeric_months}(?-i:\s*)\-|/(?-i:\s*){numeric_months}(?-i:\s*)/)(?-i:\s*){year}|{numeric_months}(?-i:\s*)(?:\-(?-i:\s*){numeric_days}(?-i:\s*)\-|/(?-i:\s*){numeric_days}(?-i:\s*)/)(?-i:\s*){year}\b numeric_days := (?i) \b[4-9]|30?|0[1-9]|1[0-9]?|2[0-9]?\b numeric_months := (?i) \b[2-9]|1[01]?|0[1-9]\b ``` Note, these rules generally cannot be compiled directly into regular expressions because the rule "references" in the descriptions, `{monthday}` and so forth, violate regular expression syntax. */ extern crate regex; #[macro_use] extern crate lazy_static; mod grammar; mod matching; mod pidgin; mod util; pub use grammar::Grammar; pub use matching::{Match, Matcher}; pub use pidgin::Pidgin;