book_building_parse_integer_2/
book_building_parse_integer_2.rs

1fn parse_unsigned_integer(parser: &mut trivet::Parser) -> trivet::errors::ParseResult<u64> {
2    let result = parser.take_while(|ch| ch.is_ascii_digit());
3    match result.parse::<u64>() {
4        Ok(number) => Ok(number),
5        Err(err) => Err(trivet::errors::error(parser.loc(), err)),
6    }
7}
8
9fn main() {
10    let mut parser = trivet::parse_from_stdin();
11    match parse_unsigned_integer(&mut parser) {
12        Ok(value) => println!("{}", value),
13        Err(err) => println!("ERROR: {}", err),
14    }
15}