Modules
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21
src/choice.rs
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21
src/choice.rs
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@ -0,0 +1,21 @@
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use crate::Parser;
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pub fn choice<'a, I, O, E>(parsers: &'a [&'a dyn Parser<I, O, E>]) -> impl Parser<I, O, E> + 'a
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where
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I: Clone,
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{
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move |input: I| {
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//TODO need a more principled way to return an error when no choices work
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let mut err = None;
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for parser in parsers.iter() {
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match parser.parse(input.clone()) {
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Ok(res) => return Ok(res),
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Err(e) => {
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err = Some(e);
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}
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}
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}
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Err(err.unwrap())
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}
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}
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61
src/lib.rs
61
src/lib.rs
@ -1,8 +1,15 @@
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#![allow(dead_code)] //TODO eventually turn this off
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mod choice;
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mod primitives;
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mod sequence;
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pub use choice::*;
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pub use primitives::*;
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pub use sequence::*;
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type ParseResult<I, O, E> = Result<(O, I), E>;
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trait Parser<I, O, E> {
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pub trait Parser<I, O, E> {
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fn parse(&self, input: I) -> ParseResult<I, O, E>;
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}
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@ -15,46 +22,6 @@ where
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}
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}
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fn literal(expected: &'static str) -> impl Fn(&str) -> ParseResult<&str, &str, &str> {
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move |input| match input.get(0..expected.len()) {
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Some(next) if next == expected => Ok((next, &input[expected.len()..])),
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_ => Err(input),
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}
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}
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fn sequence<I, O1, O2, E>(
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first: impl Parser<I, O1, E>,
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second: impl Parser<I, O2, E>,
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) -> impl Parser<I, (O1, O2), E> {
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move |input| -> ParseResult<I, (O1, O2), E> {
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first.parse(input).and_then(|(result1, rest)| {
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second
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.parse(rest)
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.map(|(result2, rest2)| ((result1, result2), rest2))
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})
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}
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}
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fn choice<'a, I, O, E>(parsers: &'a [&'a dyn Parser<I, O, E>]) -> impl Parser<I, O, E> + 'a
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where
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I: Clone,
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{
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move |input: I| {
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//TODO need a more principled way to return an error when no choices work
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let mut err = None;
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for parser in parsers.iter() {
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match parser.parse(input.clone()) {
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Ok(res) => return Ok(res),
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Err(e) => {
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err = Some(e);
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}
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}
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}
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Err(err.unwrap())
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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@ -74,4 +41,16 @@ mod tests {
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assert_eq!(output.0 .1, (" ", "jonzzz"));
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assert_eq!(output.1, "");
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}
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#[test]
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fn test_choice() {
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let a = literal("bongo");
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let b = literal("sucy");
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let c = literal("ara");
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let inputs = [&a as &dyn Parser<&str, &str, &str>, &b, &c];
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let parser = choice(&inputs);
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let output = parser.parse("ara hajimete").unwrap();
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assert_eq!(("ara", " hajimete"), output);
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}
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}
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26
src/primitives.rs
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26
src/primitives.rs
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@ -0,0 +1,26 @@
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use crate::{ParseResult, Parser};
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pub fn literal(expected: &'static str) -> impl Fn(&str) -> ParseResult<&str, &str, &str> {
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move |input| match input.get(0..expected.len()) {
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Some(next) if next == expected => Ok((next, &input[expected.len()..])),
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_ => Err(input),
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}
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}
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pub fn literal_char<'a>(expected: char) -> impl Parser<&'a str, char, &'a str> {
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move |input: &'a str| match input.chars().next() {
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Some(ch) if ch == expected => Ok((expected, &input[ch.len_utf8()..])),
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_ => Err(input),
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn literals() {
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let parser = literal_char('f');
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assert_eq!(Ok(('f', "unky")), parser.parse("funky"));
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}
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}
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14
src/sequence.rs
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14
src/sequence.rs
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@ -0,0 +1,14 @@
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use crate::{ParseResult, Parser};
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pub fn sequence<I, O1, O2, E>(
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first: impl Parser<I, O1, E>,
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second: impl Parser<I, O2, E>,
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) -> impl Parser<I, (O1, O2), E> {
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move |input| -> ParseResult<I, (O1, O2), E> {
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first.parse(input).and_then(|(result1, rest)| {
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second
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.parse(rest)
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.map(|(result2, rest2)| ((result1, result2), rest2))
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})
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}
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}
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