Macro nom::verify

macro_rules! verify {
    (__impl $i:expr, $submac:ident!( $($args:tt)* ), $submac2:ident!( $($args2:tt)* )) => { ... };
    ($i:expr, $submac:ident!( $($args:tt)* ), $g:expr) => { ... };
    ($i:expr, $submac:ident!( $($args:tt)* ), $submac2:ident!( $($args2:tt)* )) => { ... };
    ($i:expr, $f:expr, $g:expr) => { ... };
    ($i:expr, $f:expr, $submac:ident!( $($args:tt)* )) => { ... };
}

verify!(I -> IResult<I,O>, O -> bool) => I -> IResult<I, O> returns the result of the child parser if it satisfies a verifcation function

 named!(check<u32>, verify!(be_u32, |val:u32| val >= 0 && val < 3));