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use std::collections::HashMap;
use std::iter::Iterator;
use winnow::ascii::alphanumeric1;
use winnow::combinator::iterator;
use winnow::combinator::{separated_pair, terminated};
use winnow::prelude::*;
fn main() {
let mut data = "abcabcabcabc";
fn parser<'s>(i: &mut &'s str) -> ModalResult<&'s str> {
"abc".parse_next(i)
}
// `from_fn` (available from Rust 1.34) can create an iterator
// from a closure
let it = std::iter::from_fn(move || parser.parse_next(&mut data).ok());
for value in it {
println!("parser returned: {value}");
}
println!("\n********************\n");
let mut data = "abcabcabcabc";
// if `from_fn` is not available, it is possible to fold
// over an iterator of functions
let res = std::iter::repeat(parser)
.take(3)
.try_fold(Vec::new(), |mut acc, mut parser| {
parser.parse_next(&mut data).map(|o| {
acc.push(o);
acc
})
});
// will print "parser iterator returned: Ok(("abc", ["abc", "abc", "abc"]))"
println!("\nparser iterator returned: {res:?}");
println!("\n********************\n");
let data = "key1:value1,key2:value2,key3:value3,;";
// `winnow::combinator::iterator` will return an iterator
// producing the parsed values. Compared to the previous
// solutions:
// - we can work with a normal iterator like `from_fn`
// - we can get the remaining input afterwards, like with the `try_fold` trick
let mut winnow_it = iterator(
data,
terminated(separated_pair(alphanumeric1, ":", alphanumeric1), ","),
);
let res = winnow_it
.map(|(k, v)| (k.to_uppercase(), v))
.collect::<HashMap<_, _>>();
let parser_result: ModalResult<(_, _), ()> = winnow_it.finish();
let (remaining_input, ()) = parser_result.unwrap();
// will print "iterator returned {"key1": "value1", "key3": "value3", "key2": "value2"}, remaining input is ';'"
println!("iterator returned {res:?}, remaining input is '{remaining_input}'");
}
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