Macro nom::recognize

macro_rules! recognize {
    ($i:expr, $submac:ident!( $($args:tt)* )) => { ... };
    ($i:expr, $f:expr) => { ... };
}

recognize!(I -> IResult<I, O> ) => I -> IResult<I, I> if the child parser was successful, return the consumed input as produced value

 named!(x, recognize!(delimited!(tag!("<!--"), take!(5), tag!("-->"))));
 let r = x(&b"<!-- abc --> aaa"[..]);
 assert_eq!(r, Ok((&b" aaa"[..], &b"<!-- abc -->"[..])));