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use pear::{macros::*, parsers::*};
type Input<'a> = pear::input::Pear<pear::input::Text<'a>>;
type Result<'a, T> = pear::input::Result<T, Input<'a>>;
#[parser(rewind, peek)]
fn ab<'a>(input: &mut Input<'a>) -> Result<'a, ()> {
eat('a')?;
eat('b')?;
eof()?;
}
#[parser(rewind, peek)]
fn abc<'a>(input: &mut Input<'a>) -> Result<'a, ()> {
eat('a')?;
eat('b')?;
eat('c')?;
eof()?;
}
#[parser(rewind, peek)]
fn abcd<'a>(input: &mut Input<'a>) -> Result<'a, ()> {
eat('a')?;
eat('b')?;
eat('c')?;
eat('d')?;
eof()?;
}
#[parser]
fn combo<'a>(input: &mut Input<'a>) -> Result<'a, &'a str> {
switch! {
ab() => eat_slice("ab")?,
abc() => eat_slice("abc")?,
abcd() => eat_slice("abcd")?,
_ => parse_error!("not ab, abc, or abcd")?
}
}
#[test]
fn test_peeking_ab() {
let result = parse!(combo: Input::new("ab")).unwrap();
assert_eq!(result, "ab")
}
#[test]
fn test_peeking_abc() {
let result = parse!(combo: Input::new("abc")).unwrap();
assert_eq!(result, "abc")
}
#[test]
fn test_peeking_abcd() {
let result = parse!(combo: Input::new("abcd")).unwrap();
assert_eq!(result, "abcd")
}
#[test]
fn test_peeking_fail() {
let result = parse!(combo: Input::new("a"));
assert!(result.is_err());
let result = parse!(combo: Input::new("abcdef"));
assert!(result.is_err());
}
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