This commit is contained in:
Greg Shuflin 2022-10-15 23:41:22 -07:00
parent 194e23a5be
commit 3bc608d4a7

View File

@ -1,35 +1,51 @@
#![feature(assert_matches)] #![feature(assert_matches)]
#![allow(dead_code)] //TODO eventually turn this off #![allow(dead_code)] //TODO eventually turn this off
type ParseResult<I, O, E> = Result<(O, I), E>; type ParseResult<I, O, E> = Result<(O, I), E>;
trait Parser<I, O, E> { trait Parser<I, O, E> {
fn parse(&self, input: I) -> ParseResult<I, O, E>; fn parse(&self, input: I) -> ParseResult<I, O, E>;
} }
impl<I, O, E, F> Parser<I, O, E> for F where F: Fn(I) -> ParseResult<I, O, E> { impl<I, O, E, F> Parser<I, O, E> for F
where
F: Fn(I) -> ParseResult<I, O, E>,
{
fn parse(&self, input: I) -> ParseResult<I, O, E> { fn parse(&self, input: I) -> ParseResult<I, O, E> {
self(input) self(input)
} }
} }
fn literal(expected: &'static str) -> impl Fn(&str) -> ParseResult<&str, (), &str> { fn literal(expected: &'static str) -> impl Fn(&str) -> ParseResult<&str, &str, &str> {
move |input| match input.get(0..expected.len()) { move |input| match input.get(0..expected.len()) {
Some(next) if next == expected => Some(next) if next == expected => Ok((expected, &input[expected.len()..])),
Ok(((), &input[expected.len()..])), _ => Err(input),
_ => Err(input)
} }
} }
fn map<P, F, I, O1, O2, E>(parser: P, map_fn: F) -> impl Parser<I, O2, E>
where
P: Parser<I, O1, E>,
F: Fn(O1) -> O2,
{
move |input| parser.parse(input).map(|(result, rest)| (map_fn(result), rest))
}
#[cfg(test)] #[cfg(test)]
mod tests { mod tests {
use super::*; use super::*;
use std::assert_matches::assert_matches; use std::assert_matches::assert_matches;
#[test] #[test]
fn parsing() { fn test_parsing() {
let output = literal("a")("a yolo"); let output = literal("a")("a yolo");
assert_matches!(output.unwrap(), ((), " yolo")); assert_matches!(output.unwrap(), ("a", " yolo"));
}
#[test]
fn test_map() {
let lit_a = literal("a");
let output = map(lit_a, |s| s.to_uppercase()).parse("a yolo");
assert_matches!(output.unwrap(), (s, " yolo") if s == "A");
} }
} }