1use std::collections::HashMap;
2use std::iter::Iterator;
3
4use nom::bytes::complete::tag;
5use nom::character::complete::alphanumeric1;
6use nom::combinator::iterator;
7use nom::sequence::{separated_pair, terminated};
8use nom::IResult;
9
10fn main() {
11  let mut data = "abcabcabcabc";
12
13  fn parser(i: &str) -> IResult<&str, &str> {
14    tag("abc")(i)
15  }
16
17  // `from_fn` (available from Rust 1.34) can create an iterator
18  // from a closure
19  let it = std::iter::from_fn(move || {
20    match parser(data) {
21      // when successful, a nom parser returns a tuple of
22      // the remaining input and the output value.
23      // So we replace the captured input data with the
24      // remaining input, to be parsed on the next call
25      Ok((i, o)) => {
26        data = i;
27        Some(o)
28      }
29      _ => None,
30    }
31  });
32
33  for value in it {
34    println!("parser returned: {}", value);
35  }
36
37  println!("\n********************\n");
38
39  let data = "abcabcabcabc";
40
41  // if `from_fn` is not available, it is possible to fold
42  // over an iterator of functions
43  let res =
44    std::iter::repeat(parser)
45      .take(3)
46      .try_fold((data, Vec::new()), |(data, mut acc), parser| {
47        parser(data).map(|(i, o)| {
48          acc.push(o);
49          (i, acc)
50        })
51      });
52
53  // will print "parser iterator returned: Ok(("abc", ["abc", "abc", "abc"]))"
54  println!("\nparser iterator returned: {:?}", res);
55
56  println!("\n********************\n");
57
58  let data = "key1:value1,key2:value2,key3:value3,;";
59
60  // `nom::combinator::iterator` will return an iterator
61  // producing the parsed values. Compared to the previous
62  // solutions:
63  // - we can work with a normal iterator like `from_fn`
64  // - we can get the remaining input afterwards, like with the `try_fold` trick
65  let mut nom_it = iterator(
66    data,
67    terminated(
68      separated_pair(alphanumeric1, tag(":"), alphanumeric1),
69      tag(","),
70    ),
71  );
72
73  let res = nom_it
74    .map(|(k, v)| (k.to_uppercase(), v))
75    .collect::<HashMap<_, _>>();
76
77  let parser_result: IResult<_, _> = nom_it.finish();
78  let (remaining_input, ()) = parser_result.unwrap();
79
80  // will print "iterator returned {"key1": "value1", "key3": "value3", "key2": "value2"}, remaining input is ';'"
81  println!(
82    "iterator returned {:?}, remaining input is '{}'",
83    res, remaining_input
84  );
85}
86