[−][src]Macro nom::opt_res
opt_res!(I -> IResult<I,O>) => I -> IResult<I, Result<nom::Err,O>>
make the underlying parser optional.
Returns a Result
, with Err
containing the parsing error.
ⓘ
named!( o<&[u8], Result<&[u8], nom::Err<&[u8]> > >, opt_res!( tag!( "abcd" ) ) ); let a = b"abcdef"; let b = b"bcdefg"; assert_eq!(o(&a[..]), Ok((&b"ef"[..], Ok(&b"abcd"[..]))); assert_eq!(o(&b[..]), Ok((&b"bcdefg"[..], Err(error_position!(&b[..], ErrorKind::Tag))));