attempting_to_nom.rs

    fn fold_op<F: Fn(f64, f64)>(input: &[u8], init: f64, f: F) -> IResult<&[u8], f64> {
        fold_many0!(ws!(alt!(apply!(list) | apply!(f64::from_str))), init, f)
    }
    named!(list<f64>, delimited!(tag!("("), ws!(alt!(
        proceed!(tag!("+"), apply!(fop, 0.0, |acc, item| acc + item))
    )), tag!(")")));
    
    
    error: unexpected end of macro invocation
  --> src\main.rs:19:76
   |
19 |         fold_many0!(ws!(alt!(apply!(list) | apply!(f64::from_str))), init, f)
   |                                                                            ^