135 lines
3.3 KiB
Rust
135 lines
3.3 KiB
Rust
#![feature(assert_matches)]
|
|
#![allow(dead_code)] //TODO eventually turn this off
|
|
|
|
type ParseResult<I, O, E> = Result<(O, I), E>;
|
|
|
|
trait Parser<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>,
|
|
{
|
|
fn parse(&self, input: I) -> ParseResult<I, O, E> {
|
|
self(input)
|
|
}
|
|
}
|
|
|
|
fn literal(expected: &'static str) -> impl Fn(&str) -> ParseResult<&str, &str, &str> {
|
|
move |input| match input.get(0..expected.len()) {
|
|
Some(next) if next == expected => Ok((expected, &input[expected.len()..])),
|
|
_ => 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))
|
|
}
|
|
}
|
|
|
|
fn seq<P1, P2, I, O1, O2, E>(parser1: P1, parser2: P2) -> impl Parser<I, (O1, O2), E>
|
|
where
|
|
P1: Parser<I, O1, E>,
|
|
P2: Parser<I, O2, E>,
|
|
{
|
|
move |input| {
|
|
parser1.parse(input).and_then(|(result1, rest1)| {
|
|
parser2
|
|
.parse(rest1)
|
|
.map(|(result2, rest2)| ((result1, result2), rest2))
|
|
})
|
|
}
|
|
}
|
|
|
|
fn one_or_more<P, I, O>(parser: P) -> impl Parser<I, Vec<O>, I>
|
|
where
|
|
P: Parser<I, O, I>,
|
|
I: Copy,
|
|
{
|
|
move |mut input| {
|
|
let mut results = Vec::new();
|
|
|
|
if let Ok((result, rest)) = parser.parse(input) {
|
|
results.push(result);
|
|
input = rest;
|
|
} else {
|
|
return Err(input);
|
|
}
|
|
|
|
while let Ok((item, rest)) = parser.parse(input) {
|
|
results.push(item);
|
|
input = rest;
|
|
}
|
|
|
|
Ok((results, input))
|
|
}
|
|
}
|
|
|
|
/// Parses a standard identifier in a programming language
|
|
fn identifier(input: &str) -> ParseResult<&str, String, &str> {
|
|
let mut chars = input.chars();
|
|
let mut buf = String::new();
|
|
|
|
match chars.next() {
|
|
Some(ch) if ch.is_alphabetic() => buf.push(ch),
|
|
_ => return Err(input),
|
|
}
|
|
|
|
while let Some(next) = chars.next() {
|
|
if next.is_alphanumeric() {
|
|
buf.push(next);
|
|
} else {
|
|
break;
|
|
}
|
|
}
|
|
|
|
let next_index = buf.len();
|
|
Ok((buf, &input[next_index..]))
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod tests {
|
|
use super::*;
|
|
use std::assert_matches::assert_matches;
|
|
|
|
#[test]
|
|
fn test_parsing() {
|
|
let output = literal("a")("a yolo");
|
|
assert_matches!(output.unwrap(), ("a", " yolo"));
|
|
}
|
|
|
|
#[test]
|
|
fn test_identifier() {
|
|
assert_matches!(identifier("bongo1beans"), Ok((s, "")) if s == "bongo1beans");
|
|
assert_matches!(identifier("2bongo1beans"), Err("2bongo1beans"));
|
|
}
|
|
|
|
#[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");
|
|
}
|
|
|
|
#[test]
|
|
fn test_seq() {
|
|
let p = seq(identifier, seq(literal(" "), literal("ruts")));
|
|
assert_matches!(p.parse("fort1 ruts"), Ok((r, "")) if r.0 == "fort1" && r.1 == (" ", "ruts") );
|
|
}
|
|
|
|
#[test]
|
|
fn test_one_or_more() {
|
|
let p = one_or_more(literal("bongo "));
|
|
let input = "bongo bongo bongo bongo bongo ";
|
|
assert_matches!(p.parse(input), Ok((v, "")) if v.len() == 5);
|
|
}
|
|
}
|