Struct Repeat

pub struct Repeat<P, I, O, C, E>
where
    P: Parser<I, O, E>,
    I: Stream,
    C: Accumulate<O>,
    E: ParserError<I>,
{ /* private fields */ }

Customizable Parser implementation for repeat

Implementations

impl<ParseNext, Input, Output, Error> Repeat<ParseNext, Input, Output, (), Error>

where ParseNext: Parser<Input, Output, Error>, Input: Stream, Error: ParserError<Input>,

pub fn fold<Init, Op, Result>( self, init: Init, op: Op, ) -> impl Parser<Input, Result, Error>

where Init: FnMut() -> Result, Op: FnMut(Result, Output) -> Result,

Repeats the embedded parser, calling op to gather the results

This stops before n when the parser returns ErrMode::Backtrack. To instead chain an error up, see cut_err.

Arguments

• init A function returning the initial value.
• op The function that combines a result of f with the current accumulator.

Warning: If the parser passed to fold accepts empty inputs (like alpha0 or digit0), fold_repeat will return an error, to prevent going into an infinite loop.

Example

Zero or more repetitions:

use winnow::combinator::repeat;

fn parser<'i>(s: &mut &'i str) -> ModalResult<Vec<&'i str>> {
  repeat(
    0..,
    "abc"
  ).fold(
    Vec::new,
    |mut acc: Vec<_>, item| {
      acc.push(item);
      acc
    }
  ).parse_next(s)
}

assert_eq!(parser.parse_peek("abcabc"), Ok(("", vec!["abc", "abc"])));
assert_eq!(parser.parse_peek("abc123"), Ok(("123", vec!["abc"])));
assert_eq!(parser.parse_peek("123123"), Ok(("123123", vec![])));
assert_eq!(parser.parse_peek(""), Ok(("", vec![])));

One or more repetitions:

use winnow::combinator::repeat;

fn parser<'i>(s: &mut &'i str) -> ModalResult<Vec<&'i str>> {
  repeat(
    1..,
    "abc",
  ).fold(
    Vec::new,
    |mut acc: Vec<_>, item| {
      acc.push(item);
      acc
    }
  ).parse_next(s)
}

assert_eq!(parser.parse_peek("abcabc"), Ok(("", vec!["abc", "abc"])));
assert_eq!(parser.parse_peek("abc123"), Ok(("123", vec!["abc"])));
assert!(parser.parse_peek("123123").is_err());
assert!(parser.parse_peek("").is_err());

Arbitrary number of repetitions:

use winnow::combinator::repeat;

fn parser<'i>(s: &mut &'i str) -> ModalResult<Vec<&'i str>> {
  repeat(
    0..=2,
    "abc",
  ).fold(
    Vec::new,
    |mut acc: Vec<_>, item| {
      acc.push(item);
      acc
    }
  ).parse_next(s)
}

assert_eq!(parser.parse_peek("abcabc"), Ok(("", vec!["abc", "abc"])));
assert_eq!(parser.parse_peek("abc123"), Ok(("123", vec!["abc"])));
assert_eq!(parser.parse_peek("123123"), Ok(("123123", vec![])));
assert_eq!(parser.parse_peek(""), Ok(("", vec![])));
assert_eq!(parser.parse_peek("abcabcabc"), Ok(("abc", vec!["abc", "abc"])));

pub fn verify_fold<Init, Op, Result>( self, init: Init, op: Op, ) -> impl Parser<Input, Result, Error>

where Init: FnMut() -> Result, Op: FnMut(Result, Output) -> Option<Result>,

Akin to Repeat::fold, but for containers that can reject an element.

This stops before n when the parser returns ErrMode::Backtrack. To instead chain an error up, see cut_err. Additionally, if the fold function returns None, the parser will stop and return an error.

Arguments

• init A function returning the initial value.
• op The function that combines a result of f with the current accumulator.

Warning: If the parser passed to repeat accepts empty inputs (like alpha0 or digit0), verify_fold will return an error, to prevent going into an infinite loop.

Example

Guaranteeing that the input had unique elements:

use winnow::combinator::repeat;
use std::collections::HashSet;

fn parser<'i>(s: &mut &'i str) -> ModalResult<HashSet<&'i str>> {
  repeat(
    0..,
    "abc"
  ).verify_fold(
    HashSet::new,
    |mut acc: HashSet<_>, item| {
      if acc.insert(item) {
         Some(acc)
      } else {
         None
      }
    }
  ).parse_next(s)
}

assert_eq!(parser.parse_peek("abc"), Ok(("", HashSet::from(["abc"]))));
assert!(parser.parse_peek("abcabc").is_err());
assert_eq!(parser.parse_peek("abc123"), Ok(("123", HashSet::from(["abc"]))));
assert_eq!(parser.parse_peek("123123"), Ok(("123123", HashSet::from([]))));
assert_eq!(parser.parse_peek(""), Ok(("", HashSet::from([]))));

pub fn try_fold<Init, Op, OpError, Result>( self, init: Init, op: Op, ) -> impl Parser<Input, Result, Error>

where Init: FnMut() -> Result, Op: FnMut(Result, Output) -> Result<Result, OpError>, Error: FromExternalError<Input, OpError>,

Akin to Repeat::fold, but for containers that can error when an element is accumulated.

This stops before n when the parser returns ErrMode::Backtrack. To instead chain an error up, see cut_err. Additionally, if the fold function returns an error, the parser will stop and return it.

Arguments

• init A function returning the initial value.
• op The function that combines a result of f with the current accumulator.

Warning: If the parser passed to repeat accepts empty inputs (like alpha0 or digit0), try_fold will return an error, to prevent going into an infinite loop.

Example

Writing the output to a vector of bytes:

use winnow::combinator::repeat;
use std::io::Write;
use std::io::Error;

fn parser(s: &mut &str) -> ModalResult<Vec<u8>> {
  repeat(
    0..,
    "abc"
  ).try_fold(
    Vec::new,
    |mut acc, item: &str| -> Result<_, Error> {
      acc.write(item.as_bytes())?;
      Ok(acc)
    }
  ).parse_next(s)
}

assert_eq!(parser.parse_peek("abc"), Ok(("", b"abc".to_vec())));
assert_eq!(parser.parse_peek("abc123"), Ok(("123", b"abc".to_vec())));
assert_eq!(parser.parse_peek("123123"), Ok(("123123", vec![])));
assert_eq!(parser.parse_peek(""), Ok(("", vec![])));

Trait Implementations

impl<P, I, O, C, E> Parser<I, C, E> for Repeat<P, I, O, C, E>

where P: Parser<I, O, E>, I: Stream, C: Accumulate<O>, E: ParserError<I>,

fn parse_next(&mut self, i: &mut I) -> Result<C, E>

Take tokens from the Stream, turning it into the output

fn parse( &mut self, input: I, ) -> Result<O, ParseError<I, <E as ParserError<I>>::Inner>>

where Self: Sized, I: Stream + StreamIsPartial, E: ParserError<I>, <E as ParserError<I>>::Inner: ParserError<I>,

Parse all of input, generating O from it

fn parse_peek(&mut self, input: I) -> Result<(I, O), E>

Take tokens from the Stream, turning it into the output

fn by_ref(&mut self) -> ByRef<'_, Self, I, O, E>

where Self: Sized,

Treat &mut Self as a parser

fn value<O2>(self, val: O2) -> Value<Self, I, O, O2, E>

where Self: Sized, O2: Clone,

Produce the provided value

fn default_value<O2>(self) -> DefaultValue<Self, I, O, O2, E>

where Self: Sized, O2: Default,

Produce a type’s default value

fn void(self) -> Void<Self, I, O, E>

where Self: Sized,

Discards the output of the Parser

fn output_into<O2>(self) -> OutputInto<Self, I, O, O2, E>

where Self: Sized, O: Into<O2>,

Convert the parser’s output to another type using std::convert::From

fn take(self) -> Take<Self, I, O, E>

where Self: Sized, I: Stream,

Produce the consumed input as produced value.

fn with_taken(self) -> WithTaken<Self, I, O, E>

where Self: Sized, I: Stream,

Produce the consumed input with the output

fn span(self) -> Span<Self, I, O, E>

where Self: Sized, I: Stream + Location,

Produce the location of the consumed input as produced value.

fn with_span(self) -> WithSpan<Self, I, O, E>

where Self: Sized, I: Stream + Location,

Produce the location of consumed input with the output

fn map<G, O2>(self, map: G) -> Map<Self, G, I, O, O2, E>

where G: FnMut(O) -> O2, Self: Sized,

Maps a function over the output of a parser

fn try_map<G, O2, E2>(self, map: G) -> TryMap<Self, G, I, O, O2, E, E2>

where Self: Sized, G: FnMut(O) -> Result<O2, E2>, I: Stream, E: FromExternalError<I, E2> + ParserError<I>,

Applies a function returning a Result over the output of a parser.

fn verify_map<G, O2>(self, map: G) -> VerifyMap<Self, G, I, O, O2, E>

where Self: Sized, G: FnMut(O) -> Option<O2>, I: Stream, E: ParserError<I>,

Apply both Parser::verify and Parser::map.

fn flat_map<G, H, O2>(self, map: G) -> FlatMap<Self, G, H, I, O, O2, E>

where Self: Sized, G: FnMut(O) -> H, H: Parser<I, O2, E>,

Creates a parser from the output of this one

fn and_then<G, O2>(self, inner: G) -> AndThen<Self, G, I, O, O2, E>

where Self: Sized, G: Parser<O, O2, E>, O: StreamIsPartial, I: Stream,

Applies a second parser over the output of the first one

fn parse_to<O2>(self) -> ParseTo<Self, I, O, O2, E>

where Self: Sized, I: Stream, O: ParseSlice<O2>, E: ParserError<I>,

Apply std::str::FromStr to the output of the parser

fn verify<G, O2>(self, filter: G) -> Verify<Self, G, I, O, O2, E>

where Self: Sized, G: FnMut(&O2) -> bool, I: Stream, O: Borrow<O2>, O2: ?Sized, E: ParserError<I>,

Returns the output of the child parser if it satisfies a verification function.

fn context<C>(self, context: C) -> Context<Self, I, O, E, C>

where Self: Sized, I: Stream, E: AddContext<I, C> + ParserError<I>, C: Clone + Debug,

If parsing fails, add context to the error

fn complete_err(self) -> CompleteErr<Self, I, O, E>

where Self: Sized,

Transforms Incomplete into Backtrack

fn err_into<E2>(self) -> ErrInto<Self, I, O, E, E2>

where Self: Sized, E: Into<E2>,

Convert the parser’s error to another type using std::convert::From