Function combine::combinator::optional
[−]
[src]
pub fn optional<P>(parser: P) -> Optional<P> where P: Parser
Returns Some(value)
and None
on parse failure (always succeeds)
let mut parser = optional(digit()); let result1 = parser.parse("a"); assert_eq!(result1, Ok((None, "a"))); let result2 = parser.parse("1"); assert_eq!(result2, Ok((Some('1'), "")));