Function utils::parser::one_of

pub fn one_of<L: ParserList>(options: L) -> OneOf<L>

Attempt to parse using a list of parsers.

Similar to Parser::or, each parser will be tried in order until one succeeds. If no parsers succeed, the error from the parser furthest into the input is returned.

Prefer parser::literal_map if all the parsers are string literals.

Examples

#[derive(Debug, PartialEq)]
enum Value {
    Unsigned8(u8),
    Unsigned32(u32),
    Signed8(i8),
    Signed32(i32),
}

let parser = parser::one_of((
    parser::u8().map(Value::Unsigned8),
    parser::u32().map(Value::Unsigned32),
    parser::i8().map(Value::Signed8),
    parser::i32().map(Value::Signed32),
));

assert_eq!(
    parser.parse_complete("31").unwrap(),
    Value::Unsigned8(31),
);
assert_eq!(
    parser.parse_complete("4294967295").unwrap(),
    Value::Unsigned32(4294967295),
);
assert_eq!(
    parser.parse_complete("-1").unwrap(),
    Value::Signed8(-1)
);
assert_eq!(
    parser.parse_complete("-2147483648").unwrap(),
    Value::Signed32(-2147483648)
);

assert_eq!(
    parser.parse(b"not a number").unwrap_err().0,
    ParseError::Expected("unsigned integer")
);
assert_eq!(
    parser.parse(b"-4294967295").unwrap_err().0,
    ParseError::NumberTooSmall(-2147483648)
);