macro_rules! dispatch {
($match_expr: expr; $( $($pat: pat)|+ $(if $pred:expr)? => $expr: expr ),+ $(,)? ) => { ... };
}
Expand description
dispatch!
allows a parser to be constructed depending on earlier input, without forcing each
branch to have the same type of parser
use combine::{dispatch, any, token, satisfy, EasyParser, Parser};
let mut parser = any().then(|e| {
dispatch!(e;
'a' => token('a'),
'b' => satisfy(|b| b == 'b'),
t if t == 'c' => any(),
_ => token('d')
)
});
assert_eq!(parser.easy_parse("aa"), Ok(('a', "")));
assert_eq!(parser.easy_parse("cc"), Ok(('c', "")));
assert_eq!(parser.easy_parse("cd"), Ok(('d', "")));
assert!(parser.easy_parse("ab").is_err());