504 lines
14 KiB
Rust
504 lines
14 KiB
Rust
/*
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* meli - melib crate.
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*
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* Copyright 2019 Manos Pitsidianakis
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*
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* This file is part of meli.
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*
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* meli is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* meli is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with meli. If not, see <http://www.gnu.org/licenses/>.
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*/
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//! Parser combinators.
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pub type Result<'a, Output> = std::result::Result<(&'a str, Output), &'a str>;
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pub trait Parser<'a, Output> {
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fn parse(&self, input: &'a str) -> Result<'a, Output>;
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fn parse_complete(&self, input: &'a str) -> Result<'a, Output> {
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match self.parse(input) {
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r @ Ok(("", _)) => r,
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r @ Err(_) => r,
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Ok(_) => Err(input),
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}
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}
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fn map<F, NewOutput>(self, map_fn: F) -> BoxedParser<'a, NewOutput>
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where
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Self: Sized + 'a,
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Output: 'a,
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NewOutput: 'a,
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F: Fn(Output) -> NewOutput + 'a,
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{
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BoxedParser::new(map(self, map_fn))
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}
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fn and_then<F, NextParser, NewOutput>(self, f: F) -> BoxedParser<'a, NewOutput>
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where
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Self: Sized + 'a,
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Output: 'a,
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NewOutput: 'a,
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NextParser: Parser<'a, NewOutput> + 'a,
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F: Fn(Output) -> NextParser + 'a,
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{
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BoxedParser::new(and_then(self, f))
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}
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}
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pub fn left<'a, P1, P2, R1, R2>(parser1: P1, parser2: P2) -> impl Parser<'a, R1>
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where
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P1: Parser<'a, R1>,
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P2: Parser<'a, R2>,
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{
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map(pair(parser1, parser2), |(left, _right)| left)
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}
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pub fn right<'a, P1, P2, R1, R2>(parser1: P1, parser2: P2) -> impl Parser<'a, R2>
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where
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P1: Parser<'a, R1>,
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P2: Parser<'a, R2>,
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{
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map(pair(parser1, parser2), |(_left, right)| right)
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}
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impl<'a, F, Output> Parser<'a, Output> for F
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where
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F: Fn(&'a str) -> Result<Output>,
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{
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fn parse(&self, input: &'a str) -> Result<'a, Output> {
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self(input)
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}
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}
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pub fn map<'a, P, F, A, B>(parser: P, map_fn: F) -> impl Parser<'a, B>
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where
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P: Parser<'a, A>,
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F: Fn(A) -> B,
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{
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move |input| {
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parser
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.parse(input)
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.map(|(next_input, result)| (next_input, map_fn(result)))
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}
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}
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pub fn match_literal<'a>(expected: &'static str) -> impl Parser<'a, ()> {
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move |input: &'a str| match input.get(0..expected.len()) {
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Some(next) if next == expected => Ok((&input[expected.len()..], ())),
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_ => Err(input),
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}
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}
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pub fn match_literal_anycase<'a>(expected: &'static str) -> impl Parser<'a, ()> {
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move |input: &'a str| match input.get(0..expected.len()) {
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Some(next) if next.eq_ignore_ascii_case(expected) => Ok((&input[expected.len()..], ())),
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_ => Err(input),
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}
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}
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pub fn one_or_more<'a, P, A>(parser: P) -> impl Parser<'a, Vec<A>>
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where
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P: Parser<'a, A>,
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{
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move |mut input| {
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let mut result = Vec::new();
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if let Ok((next_input, first_item)) = parser.parse(input) {
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input = next_input;
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result.push(first_item);
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} else {
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return Err(input);
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}
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while let Ok((next_input, next_item)) = parser.parse(input) {
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input = next_input;
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result.push(next_item);
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}
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Ok((input, result))
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}
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}
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pub fn zero_or_more<'a, P, A>(parser: P) -> impl Parser<'a, Vec<A>>
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where
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P: Parser<'a, A>,
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{
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move |mut input| {
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let mut result = Vec::new();
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while let Ok((next_input, next_item)) = parser.parse(input) {
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input = next_input;
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result.push(next_item);
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}
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Ok((input, result))
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}
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}
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pub fn pred<'a, P, A, F>(parser: P, predicate: F) -> impl Parser<'a, A>
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where
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P: Parser<'a, A>,
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F: Fn(&A) -> bool,
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{
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move |input| {
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if let Ok((next_input, value)) = parser.parse(input) {
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if predicate(&value) {
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return Ok((next_input, value));
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}
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}
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Err(input)
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}
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}
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pub fn whitespace_char<'a>() -> impl Parser<'a, char> {
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pred(any_char, |c| c.is_whitespace())
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}
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pub fn quoted_string<'a>() -> impl Parser<'a, String> {
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map(
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right(
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match_literal("\""),
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left(
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zero_or_more(pred(any_char, |c| *c != '"')),
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match_literal("\""),
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),
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),
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|chars| chars.into_iter().collect(),
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)
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}
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pub struct BoxedParser<'a, Output> {
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parser: Box<dyn Parser<'a, Output> + 'a>,
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}
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impl<'a, Output> BoxedParser<'a, Output> {
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fn new<P>(parser: P) -> Self
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where
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P: Parser<'a, Output> + 'a,
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{
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BoxedParser {
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parser: Box::new(parser),
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}
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}
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}
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impl<'a, Output> Parser<'a, Output> for BoxedParser<'a, Output> {
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fn parse(&self, input: &'a str) -> Result<'a, Output> {
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self.parser.parse(input)
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}
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}
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pub fn either<'a, P1, P2, A>(parser1: P1, parser2: P2) -> impl Parser<'a, A>
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where
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P1: Parser<'a, A>,
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P2: Parser<'a, A>,
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{
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move |input| match parser1.parse(input) {
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ok @ Ok(_) => ok,
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Err(_) => parser2.parse(input),
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}
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}
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pub fn whitespace_wrap<'a, P, A>(parser: P) -> impl Parser<'a, A>
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where
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P: Parser<'a, A>,
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{
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right(space0(), left(parser, space0()))
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}
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pub use whitespace_wrap as ws_eat;
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pub fn pair<'a, P1, P2, R1, R2>(parser1: P1, parser2: P2) -> impl Parser<'a, (R1, R2)>
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where
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P1: Parser<'a, R1>,
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P2: Parser<'a, R2>,
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{
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move |input| {
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parser1.parse(input).and_then(|(next_input, result1)| {
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parser2
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.parse(next_input)
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.map(|(last_input, result2)| (last_input, (result1, result2)))
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})
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}
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}
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pub fn prefix<'a, PN, P, R, RN>(pre: PN, parser: P) -> impl Parser<'a, R>
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where
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PN: Parser<'a, RN>,
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P: Parser<'a, R>,
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{
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move |input| {
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pre.parse(input).and_then(|(last_input, _)| {
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parser
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.parse(last_input)
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.map(|(rest, result)| (rest, result))
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})
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}
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}
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pub fn suffix<'a, PN, P, R, RN>(parser: P, suf: PN) -> impl Parser<'a, R>
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where
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PN: Parser<'a, RN>,
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P: Parser<'a, R>,
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{
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move |input| {
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parser
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.parse(input)
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.and_then(|(last_input, result)| suf.parse(last_input).map(|(rest, _)| (rest, result)))
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}
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}
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pub fn delimited<'a, PN, RN, P, R>(lparser: PN, mid: P, rparser: PN) -> impl Parser<'a, R>
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where
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PN: Parser<'a, RN>,
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P: Parser<'a, R>,
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{
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move |input| {
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lparser.parse(input).and_then(|(next_input, _)| {
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mid.parse(next_input).and_then(|(last_input, result)| {
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rparser.parse(last_input).map(|(rest, _)| (rest, result))
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})
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})
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}
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}
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pub fn any_char(input: &str) -> Result<char> {
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match input.chars().next() {
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Some(next) => Ok((&input[next.len_utf8()..], next)),
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_ => Err(input),
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}
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}
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pub fn string<'a>() -> impl Parser<'a, String> {
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one_or_more(pred(any_char, |c| c.is_alphanumeric())).map(|r| r.into_iter().collect())
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}
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pub fn space1<'a>() -> impl Parser<'a, Vec<char>> {
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one_or_more(whitespace_char())
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}
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pub fn space0<'a>() -> impl Parser<'a, Vec<char>> {
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zero_or_more(whitespace_char())
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}
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pub fn and_then<'a, P, F, A, B, NextP>(parser: P, f: F) -> impl Parser<'a, B>
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where
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P: Parser<'a, A>,
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NextP: Parser<'a, B>,
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F: Fn(A) -> NextP,
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{
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move |input| match parser.parse(input) {
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Ok((next_input, result)) => f(result).parse(next_input),
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Err(err) => Err(err),
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}
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}
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pub fn opt<'a, P, A>(opt_parser: P) -> impl Parser<'a, Option<A>>
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where
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P: Parser<'a, A>,
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{
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move |input| match opt_parser.parse(input) {
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Ok((next_input, result)) => Ok((next_input, Some(result))),
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Err(_) => Ok((input, None)),
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}
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}
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pub fn peek<'a, P, A>(parser: P) -> impl Parser<'a, A>
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where
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P: Parser<'a, A>,
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{
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move |input| match parser.parse(input) {
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Ok((_, result)) => Ok((input, result)),
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e @ Err(_) => e,
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}
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}
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pub fn take_until<'a, A, P>(end: P) -> impl Parser<'a, &'a str>
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where
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P: Parser<'a, A>,
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{
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move |input: &'a str| {
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let mut offset = 0;
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while !input[offset..].is_empty() {
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if let Ok((rest, _)) = end.parse(&input[offset..]) {
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return Ok((
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rest,
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&input[..(offset + input[offset..].len() - rest.len())],
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));
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}
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while offset != input.len() {
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offset += 1;
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if input.is_char_boundary(offset) {
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break;
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}
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}
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}
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Ok((&input[offset..], input))
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}
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}
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pub fn separated_list0<'a, P, A, S, Sep>(
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parser: P,
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separator: S,
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terminated: bool,
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) -> impl Parser<'a, Vec<A>>
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where
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P: Parser<'a, A>,
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S: Parser<'a, Sep>,
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{
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move |mut input| {
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let mut result = Vec::new();
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let mut prev_sep_result = Ok(());
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let mut last_item_input = input;
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while let Ok((next_input, next_item)) = parser.parse(input) {
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prev_sep_result?;
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input = next_input;
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last_item_input = next_input;
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result.push(next_item);
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match separator.parse(input) {
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Ok((next_input, _)) => {
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input = next_input;
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}
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Err(err) => {
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prev_sep_result = Err(err);
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}
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}
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}
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if !terminated {
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input = last_item_input;
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}
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Ok((input, result))
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}
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}
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#[cfg(test)]
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mod test {
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use super::*;
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use std::collections::HashMap;
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#[test]
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fn test_parsec() {
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#[derive(Debug, PartialEq)]
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enum JsonValue {
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JsonString(String),
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JsonNumber(f64),
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JsonBool(bool),
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JsonNull,
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JsonObject(HashMap<String, JsonValue>),
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JsonArray(Vec<JsonValue>),
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}
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fn parse_value<'a>() -> impl Parser<'a, JsonValue> {
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move |input| {
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either(
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either(
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either(
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either(
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either(
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map(parse_bool(), |b| JsonValue::JsonBool(b)),
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map(parse_null(), |()| JsonValue::JsonNull),
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),
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map(parse_array(), |vec| JsonValue::JsonArray(vec)),
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),
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map(parse_object(), |obj| JsonValue::JsonObject(obj)),
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),
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map(parse_number(), |n| JsonValue::JsonNumber(n)),
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),
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map(quoted_string(), |s| JsonValue::JsonString(s)),
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)
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.parse(input)
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}
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}
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fn parse_number<'a>() -> impl Parser<'a, f64> {
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move |input| {
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either(
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map(match_literal("TRUE"), |()| 1.0),
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map(match_literal("FALSe"), |()| 1.0),
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)
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.parse(input)
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}
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}
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fn parse_bool<'a>() -> impl Parser<'a, bool> {
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move |input| {
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ws_eat(either(
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map(match_literal("true"), |()| true),
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map(match_literal("false"), |()| false),
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))
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.parse(input)
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}
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}
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fn parse_null<'a>() -> impl Parser<'a, ()> {
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move |input| ws_eat(match_literal("null")).parse(input)
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}
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fn parse_array<'a>() -> impl Parser<'a, Vec<JsonValue>> {
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move |input| {
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delimited(
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ws_eat(match_literal("[")),
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separated_list0(parse_value(), ws_eat(match_literal(",")), false),
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ws_eat(match_literal("]")),
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)
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.parse(input)
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}
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}
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fn parse_object<'a>() -> impl Parser<'a, HashMap<String, JsonValue>> {
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move |input| {
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map(
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delimited(
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ws_eat(match_literal("{")),
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separated_list0(
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pair(
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suffix(quoted_string(), ws_eat(match_literal(":"))),
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parse_value(),
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),
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ws_eat(match_literal(",")),
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false,
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),
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ws_eat(match_literal("}")),
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),
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|vec: Vec<(String, JsonValue)>| vec.into_iter().collect(),
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)
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.parse(input)
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}
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}
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assert_eq!(
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Ok(("", JsonValue::JsonString("a".to_string()))),
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parse_value().parse(r#""a""#)
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);
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assert_eq!(
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Ok(("", JsonValue::JsonBool(true))),
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parse_value().parse(r#"true"#)
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);
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assert_eq!(
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Ok(("", JsonValue::JsonObject(HashMap::default()))),
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parse_value().parse(r#"{}"#)
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);
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println!("{:?}", parse_value().parse(r#"{"a":true}"#));
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println!("{:?}", parse_value().parse(r#"{"a":true,"b":false}"#));
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println!("{:?}", parse_value().parse(r#"{ "a" : true,"b": false }"#));
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println!("{:?}", parse_value().parse(r#"{ "a" : true,"b": false,}"#));
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println!("{:?}", parse_value().parse(r#"{"a":false,"b":false,}"#));
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// Line:0 Col:18 Error parsing object
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// { "a":1, "b" : 2, }
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// ^Unexpected ','
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}
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}
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