Mercurial > lbo > hg > rcombinators
view src/combinators.rs @ 6:7873119002f7
Implement Transform combinator.
author | Lewin Bormann <lewin@lewin-bormann.info> |
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date | Thu, 30 May 2019 14:27:11 +0200 |
parents | fe1259c95911 |
children | 1f30f2d25d5e |
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use crate::parser::{ParseError, ParseResult, Parser}; use crate::state::ParseState; /// Transform applies a function (which may fail) to the result of a parser. Transform only /// succeeds if the applied function succeeds, too. pub struct Transform<R, R2, P: Parser<Result = R>, F: Fn(R) -> ParseResult<R2>> { f: F, p: P, } impl<R, R2, P: Parser<Result = R>, F: Fn(R) -> ParseResult<R2>> Transform<R, R2, P, F> { pub fn new(p: P, f: F) -> Transform<R, R2, P, F> { Transform { f: f, p: p } } } impl<R, R2, P: Parser<Result = R>, F: Fn(R) -> ParseResult<R2>> Parser for Transform<R, R2, P, F> { type Result = R2; fn parse( &mut self, st: &mut ParseState<impl Iterator<Item = char>>, ) -> ParseResult<Self::Result> { match self.p.parse(st) { Ok(o) => (self.f)(o), Err(e) => Err(e), } } } pub struct Alternative<T>(T); impl<T> Alternative<T> { pub fn new(tuple: T) -> Alternative<T> { Alternative(tuple) } } macro_rules! alt_impl { ( ( $($ptype:ident/$ix:tt),* ) ) => { impl<R, $($ptype : Parser<Result=R>, )*> Parser for Alternative<($($ptype,)*)> { type Result = R; fn parse(&mut self, st: &mut ParseState<impl Iterator<Item = char>>) -> ParseResult<Self::Result> { $( let hold = st.hold(); match (self.0).$ix.parse(st) { Err(_) => (), Ok(o) => { st.release(hold); return Ok(o) } } st.reset(hold); )* return Err(ParseError::Fail("no alternative matched", st.index())) } } } } alt_impl!((P0 / 0, P1 / 1)); alt_impl!((P0 / 0, P1 / 1, P2 / 2)); alt_impl!((P0 / 0, P1 / 1, P2 / 2, P3 / 3)); alt_impl!((P0 / 0, P1 / 1, P2 / 2, P3 / 3, P4 / 4)); alt_impl!((P0 / 0, P1 / 1, P2 / 2, P3 / 3, P4 / 4, P5 / 5)); alt_impl!((P0 / 0, P1 / 1, P2 / 2, P3 / 3, P4 / 4, P5 / 5, P6 / 6)); alt_impl!(( P0 / 0, P1 / 1, P2 / 2, P3 / 3, P4 / 4, P5 / 5, P6 / 6, P7 / 7 )); alt_impl!(( P0 / 0, P1 / 1, P2 / 2, P3 / 3, P4 / 4, P5 / 5, P6 / 6, P7 / 7, P8 / 8 )); alt_impl!(( P0 / 0, P1 / 1, P2 / 2, P3 / 3, P4 / 4, P5 / 5, P6 / 6, P7 / 7, P8 / 8, P9 / 9 )); /// Sequence concatenates parsers and only succeeds if all of them do. T is always a tuple in order /// for Sequence to implement the Parser trait. The result is a tuple of all the parser results. /// /// Individual parsers need to have result types implementing Default. pub struct Sequence<T>(T); macro_rules! sequence { ($($p:expr),+) => { Sequence::new(($($p),*)) }; ($p:expr) => { $p }; } impl<T> Sequence<T> { pub fn new(tuple: T) -> Sequence<T> { Sequence(tuple) } } /// Macro for implementing sequence parsers for arbitrary tuples. Not for public use. macro_rules! seq_impl { ( ( $($ptype:ident/$ix:tt),+ ) ) => { impl<$($ptype : Parser<Result=impl Default>, )*> Parser for Sequence<($($ptype,)*)> { type Result = ($($ptype::Result,)*); fn parse(&mut self, st: &mut ParseState<impl Iterator<Item = char>>) -> ParseResult<Self::Result> { let hold = st.hold(); let mut result = Self::Result::default(); $( let r = (self.0).$ix.parse(st); if r.is_err() { st.reset(hold); return Err(r.err().unwrap()); } result.$ix = r.unwrap(); )* st.release(hold); return Ok(result); } } } } seq_impl!((P0 / 0, P1 / 1)); seq_impl!((P0 / 0, P1 / 1, P2 / 2)); seq_impl!((P0 / 0, P1 / 1, P2 / 2, P3 / 3)); seq_impl!((P0 / 0, P1 / 1, P2 / 2, P3 / 3, P4 / 4)); seq_impl!((P0 / 0, P1 / 1, P2 / 2, P3 / 3, P4 / 4, P5 / 5)); seq_impl!((P0 / 0, P1 / 1, P2 / 2, P3 / 3, P4 / 4, P5 / 5, P6 / 6)); seq_impl!(( P0 / 0, P1 / 1, P2 / 2, P3 / 3, P4 / 4, P5 / 5, P6 / 6, P7 / 7 )); seq_impl!(( P0 / 0, P1 / 1, P2 / 2, P3 / 3, P4 / 4, P5 / 5, P6 / 6, P7 / 7, P8 / 8 )); seq_impl!(( P0 / 0, P1 / 1, P2 / 2, P3 / 3, P4 / 4, P5 / 5, P6 / 6, P7 / 7, P8 / 8, P9 / 9 )); #[cfg(test)] mod tests { use super::*; use crate::parser::Parser; use crate::primitives::*; #[test] fn test_pair() { let mut p = Sequence::new((Int, StringParser::new(" aba".to_string()))); let mut ps = ParseState::new("123 aba"); assert_eq!(Ok((123, " aba".to_string())), p.parse(&mut ps)); } #[test] fn test_long_seq() { let s = || StringParser::new("a"); let mut p = Sequence::new((s(), s(), s(), s(), s(), s(), s(), s(), s(), s())); let mut ps = ParseState::new("aaaaaaaaaa"); assert_eq!( Ok(( "a".to_string(), "a".to_string(), "a".to_string(), "a".to_string(), "a".to_string(), "a".to_string(), "a".to_string(), "a".to_string(), "a".to_string(), "a".to_string() )), p.parse(&mut ps) ); } #[test] fn test_alternative() { let mut p = Alternative::new(( StringParser::new("ab"), StringParser::new("de"), StringParser::new(" "), Transform::new(Int, |i| Ok(i.to_string())), )); let mut ps = ParseState::new("de 34"); assert_eq!(Ok("de".to_string()), p.parse(&mut ps)); assert_eq!(Ok(" ".to_string()), p.parse(&mut ps)); assert_eq!(Ok("34".to_string()), p.parse(&mut ps)); } }