Struct rcombinators::combinators::Maybe

pub struct Maybe<Inner: Parser> { /* fields omitted */ }

Maybe is a combinator returning Option for a parser returning T, meaning it does not stop parsing if an optional input was not encountered. It is very similar to a Repeat parser with RepeatSpec::Max(1).

Methods

impl<Inner: Parser> Maybe<Inner>

pub fn new(p: Inner) -> Maybe<Inner>

Trait Implementations

impl<R, P: Parser<Result = R>> Parser for Maybe<P>

type Result = Option<R>

fn parse(
    &mut self,
    st: &mut ParseState<impl Iterator<Item = char>>
) -> ParseResult<Self::Result>

parse consumes input from st and returns a result or an error.

fn apply<R2, F: Fn(Self::Result) -> ParseResult<R2>>(
    self,
    f: F
) -> Transform<Self::Result, R2, Self, F> where
    Self: Sized, 

apply transforms the result of this parser using a Transform combinator.

fn then<R2, P: Parser<Result = R2>>(self, p: P) -> Then<Self, P> where
    Self: Sized, 

then attempts to parse input, and if it succeeds, executes parser p, only returning p's result. This is useful for chaining parsers of which the results are not need.