Macro sequence 

macro_rules! sequence {
    ($first:tt $(> $tail:tt)+ => $map:expr) => { ... };
    ($first:tt $(> $tail:tt)+) => { ... };
    (@chain $head:tt > $($tail:tt)+) => { ... };
    (@chain $last:tt) => { ... };
}

Macro for ergonomic parsing in sequence.

This macro recursively combines multiple parser or literals into a sequene parser using pseq. Optionally one can use => along with a closure to map the parser result into a useful result.

See select! for details about passing parser versus literals.

Examples

use cypress::prelude::*;

let input = "1+2".into_input();

#[derive(PartialEq, Debug)]
enum Expr {
    Num(u8),
    Add(Box<Expr>, Box<Expr>)
};

let parser = sequence!(
    (pnum()) > '+' > (pnum()) => |(a, (_, b))| Expr::Add(Box::new(Expr::Num(a)), Box::new(Expr::Num(b)))
);

match parser.parse(input) {
    Ok(PSuccess {val, rest: _ }) => assert_eq!(val, Expr::Add(Box::new(Expr::Num(b'1')), Box::new(Expr::Num(b'2')))),
    Err(_) => assert!(false),
};