monorepo/nom-training/src/lib.rs

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// Write two separate parser functions
// One function returns `impl Parser<>`
// The other function returns `FnMut(I) -> IResult<I, ...`
// Test each with the `map` function and the `parse` function
use nom::{character::complete::digit1, error::ParseError, IResult, Parser};
#[derive(Clone, Copy, Debug, PartialEq)]
struct Container(i32);
#[allow(dead_code)]
fn parse_container_a<'a, E: ParseError<&'a str>>(
mut parser: impl Parser<&'a str, i32, E>,
) -> impl FnMut(&'a str) -> IResult<&'a str, Container, E> {
move |input| {
let (input, value) = parser.parse(input)?;
Ok((input, Container(value)))
}
}
/*
// This form doesn't work. It is not possible in this case to get the ownership
// declarations correct on parser. The reason I would want to do this is for more
// concise representation of parse_container_a. It probably fails because map consumes
// the parser.
fn parse_container_b<'a, E: ParseError<&'a str>, P>(
mut parser: P,
) -> impl Parser<&'a str, Container, E>
where
P: Parser<&'a str, i32, E>,
{
move |input| parser.map(|val| Container(val)).parse(input)
}
*/
#[allow(dead_code)]
fn parse_container_c<'a, E: ParseError<&'a str>>(
parser: impl Parser<&'a str, i32, E>,
) -> impl Parser<&'a str, Container, E> {
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parser.map(Container)
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}
/*
// This form also doesn't work, for the same reason as parse_container_b doesn't work.
fn parse_container_d<'a, E: ParseError<&'a str>>(
parser: impl Parser<&'a str, i32, E>,
) -> impl FnMut(&'a str) -> IResult<&'a str, Container, E> {
|input| parser.map(|val| Container(val)).parse(input)
}
*/
// If I really want to do forms b and d, this works. I do the parser combination before
// creating the resulting function.
#[allow(dead_code)]
fn parse_container_e<'a, E: ParseError<&'a str>>(
parser: impl Parser<&'a str, i32, E>,
) -> impl Parser<&'a str, Container, E> {
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let mut parser = parser.map(Container);
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move |input| parser.parse(input)
}
#[allow(dead_code)]
fn parse_number_a<'a, E: ParseError<&'a str>>() -> impl FnMut(&'a str) -> IResult<&'a str, i32, E> {
parse_number
}
#[allow(dead_code)]
fn parse_number_b<'a, E: ParseError<&'a str>>() -> impl Parser<&'a str, i32, E> {
parse_number
}
#[allow(dead_code)]
fn parse_number<'a, E: ParseError<&'a str>>(input: &'a str) -> IResult<&'a str, i32, E> {
let (input, val) = digit1(input)?;
Ok((input, val.parse::<i32>().unwrap()))
}
#[cfg(test)]
mod tests {
use super::*;
use cool_asserts::assert_matches;
const DATA: &'static str = "15";
#[test]
fn function() {
let resp = parse_number_a::<nom::error::VerboseError<&str>>()
.map(|val| Container(val))
.parse(DATA);
assert_matches!(resp, Ok((_, content)) =>
assert_eq!(content, Container(15))
);
}
#[test]
fn parser() {
let resp = parse_number_b::<nom::error::VerboseError<&str>>()
.map(|val| Container(val))
.parse(DATA);
assert_matches!(resp, Ok((_, content)) =>
assert_eq!(content, Container(15))
);
}
#[test]
fn parser_composition_a() {
let resp =
parse_container_a::<nom::error::VerboseError<&str>>(parse_number_a()).parse(DATA);
assert_matches!(resp, Ok((_, content)) =>
assert_eq!(content, Container(15))
);
}
#[test]
fn parser_composition_c() {
let resp =
parse_container_c::<nom::error::VerboseError<&str>>(parse_number_b()).parse(DATA);
assert_matches!(resp, Ok((_, content)) =>
assert_eq!(content, Container(15))
);
}
}