Struct combine::parser::choice::Optional

pub struct Optional<P>(_);

Trait Implementations

impl<P: Clone> Clone for Optional<P>

fn clone(&self) -> Optional<P>

Returns a copy of the value.

pub fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<P: Copy> Copy for Optional<P>

impl<P> Parser for Optional<P> where
    P: Parser, 

type Input = P::Input

The type which is taken as input for the parser. The type must implement the Stream trait which allows the parser to read items from the type.

type Output = Option<P::Output>

The type which is returned if the parser is successful.

type PartialState = P::PartialState

Determines the state necessary to resume parsing after more input is supplied.

fn parse_partial(
    &mut self,
    input: &mut Self::Input,
    state: &mut Self::PartialState
) -> ConsumedResult<Self::Output, Self::Input>

Parses using the stream input and allows itself to be resumed at a later point using parse_partial by storing the necessary intermediate state in state

fn parse_first(
    &mut self,
    input: &mut Self::Input,
    state: &mut Self::PartialState
) -> ConsumedResult<Self::Output, Self::Input>

Parses using the stream input and allows itself to be resumed at a later point using parse_partial by storing the necessary intermediate state in state.

fn parse_mode_impl<M>(
    &mut self,
    mode: M,
    input: &mut Self::Input,
    state: &mut Self::PartialState
) -> ConsumedResult<Self::Output, Self::Input> where
    M: ParseMode, 

fn add_error(&mut self, error: &mut Tracked<<Self::Input as StreamOnce>::Error>)

Adds the first error that would normally be returned by this parser if it failed with an EmptyErr result.

fn parser_count(&self) -> ErrorOffset

fn easy_parse<I>(
    &mut self,
    input: I
) -> Result<(Self::Output, I), ParseError<I>> where
    I: Stream,
    Stream<I>: StreamOnce<Item = I::Item, Range = I::Range, Error = ParseError<Stream<I>>, Position = I::Position>,
    I::Position: Default,
    Self: Sized + Parser<Input = Stream<I>>, 

Entry point of the parser. Takes some input and tries to parse it, returning an easy to use and format error if parsing did not succeed.

fn parse(
    &mut self,
    input: Self::Input
) -> Result<(Self::Output, Self::Input), <Self::Input as StreamOnce>::Error>

Entry point of the parser. Takes some input and tries to parse it.

fn parse_with_state(
    &mut self,
    input: &mut Self::Input,
    state: &mut Self::PartialState
) -> Result<Self::Output, <Self::Input as StreamOnce>::Error>

Entry point of the parser when using partial parsing. Takes some input and tries to parse it.

fn parse_stream(
    &mut self,
    input: &mut Self::Input
) -> ParseResult<Self::Output, Self::Input>

Parses using the stream input by calling Stream::uncons one or more times.

fn parse_stream_consumed(
    &mut self,
    input: &mut Self::Input
) -> ConsumedResult<Self::Output, Self::Input>

Parses using the stream input by calling Stream::uncons one or more times.

fn parse_stream_consumed_partial(
    &mut self,
    input: &mut Self::Input,
    state: &mut Self::PartialState
) -> ConsumedResult<Self::Output, Self::Input>

fn parse_lazy(
    &mut self,
    input: &mut Self::Input
) -> ConsumedResult<Self::Output, Self::Input>

Parses using the stream input by calling Stream::uncons one or more times.

fn by_ref(&mut self) -> &mut Self where
    Self: Sized, 

Borrows a parser instead of consuming it.

fn with<P2>(self, p: P2) -> With<Self, P2> where
    Self: Sized,
    P2: Parser<Input = Self::Input>, 

Discards the value of the self parser and returns the value of p. Fails if any of the parsers fails.

fn skip<P2>(self, p: P2) -> Skip<Self, P2> where
    Self: Sized,
    P2: Parser<Input = Self::Input>, 

Discards the value of the p parser and returns the value of self. Fails if any of the parsers fails.

fn and<P2>(self, p: P2) -> (Self, P2) where
    Self: Sized,
    P2: Parser<Input = Self::Input>, 

Parses with self followed by p. Succeeds if both parsers succeed, otherwise fails. Returns a tuple with both values on success.

fn or<P2>(self, p: P2) -> Or<Self, P2> where
    Self: Sized,
    P2: Parser<Input = Self::Input, Output = Self::Output>, 

Returns a parser which attempts to parse using self. If self fails without consuming any input it tries to consume the same input using p.

fn then<N, F>(self, f: F) -> Then<Self, F> where
    Self: Sized,
    F: FnMut(Self::Output) -> N,
    N: Parser<Input = Self::Input>, 

Parses using self and then passes the value to f which returns a parser used to parse the rest of the input.

fn then_partial<N, F>(self, f: F) -> ThenPartial<Self, F> where
    Self: Sized,
    F: FnMut(&mut Self::Output) -> N,
    N: Parser<Input = Self::Input>, 

Variant of then which parses using self and then passes the value to f as a &mut reference.

fn map<F, B>(self, f: F) -> Map<Self, F> where
    Self: Sized,
    F: FnMut(Self::Output) -> B, 

Uses f to map over the parsed value.

fn flat_map<F, B>(self, f: F) -> FlatMap<Self, F> where
    Self: Sized,
    F: FnMut(Self::Output) -> Result<B, <Self::Input as StreamOnce>::Error>, 

Uses f to map over the output of self. If f returns an error the parser fails.

fn message<S>(self, msg: S) -> Message<Self> where
    Self: Sized,
    S: Into<Info<<Self::Input as StreamOnce>::Item, <Self::Input as StreamOnce>::Range>>, 

Parses with self and if it fails, adds the message msg to the error.

fn expected<S>(self, msg: S) -> Expected<Self> where
    Self: Sized,
    S: Into<Info<<Self::Input as StreamOnce>::Item, <Self::Input as StreamOnce>::Range>>, 

Parses with self and if it fails without consuming any input any expected errors are replaced by msg. msg is then used in error messages as “Expected msg”.

fn silent(self) -> Silent<Self> where
    Self: Sized, 

Parses with self, if it fails without consuming any input any expected errors that would otherwise be emitted by self are suppressed.

fn and_then<F, O, E, I>(self, f: F) -> AndThen<Self, F> where
    Self: Parser<Input = I> + Sized,
    F: FnMut(Self::Output) -> Result<O, E>,
    I: Stream,
    E: Into<<I::Error as ParseError<I::Item, I::Range, I::Position>>::StreamError>, 

Parses with self and applies f on the result if self parses successfully. f may optionally fail with an error which is automatically converted to a ParseError.

fn iter(
    self,
    input: &mut Self::Input
) -> Iter<'_, Self, Self::PartialState, FirstMode> where
    Self: Parser + Sized, 

Creates an iterator from a parser and a state. Can be used as an alternative to many when collecting directly into a Extend type is not desirable.

fn partial_iter<'a, 's, M>(
    self,
    mode: M,
    input: &'a mut Self::Input,
    partial_state: &'s mut Self::PartialState
) -> Iter<'a, Self, &'s mut Self::PartialState, M> where
    Self: Parser + Sized,
    M: ParseMode, 

Creates an iterator from a parser and a state. Can be used as an alternative to many when collecting directly into a Extend type is not desirable.

fn boxed<'a>(
    self
) -> Box<dyn Parser<Input = Self::Input, Output = Self::Output, PartialState = Self::PartialState> + 'a> where
    Self: Sized + 'a, 

Turns the parser into a trait object by putting it in a Box. Can be used to easily return parsers from functions without naming the type.

fn left<R>(self) -> Either<Self, R> where
    Self: Sized,
    R: Parser<Input = Self::Input, Output = Self::Output>, 

Wraps the parser into the Either enum which allows combinators such as then to return multiple different parser types (merging them to one)

fn right<L>(self) -> Either<L, Self> where
    Self: Sized,
    L: Parser<Input = Self::Input, Output = Self::Output>, 

Wraps the parser into the Either enum which allows combinators such as then to return multiple different parser types (merging them to one)