Macro nom::flat_map

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

flat_map!(R -> IResult<R,S>, S -> IResult<S,T>) => R -> IResult<R, T>

combines a parser R -> IResult<R,S> and a parser S -> IResult<S,T> to return another parser R -> IResult<R,T>

use nom::number::complete::recognize_float;

named!(parser<&str, f64>, flat_map!(recognize_float, parse_to!(f64)));

assert_eq!(parser("123.45;"), Ok((";", 123.45)));
assert_eq!(parser("abc"), Err(Err::Error(("abc", ErrorKind::Char))));