Rust Nom:输入的多个和结尾

Question

我正在尝试熟悉Nom，目前是版本5，其中没有CompleteStr和其他东西，所以相关问题没有太大帮助。

我如何解析像这样的东西呢？

"@pook Some free text @another_pook And another text"

转到

vec![("pook", "Some free text"), ("another_pook", "And another text")]

前缀的字符串称为“字段标识符”；下一个子字符串是描述；两者都称为“@”。

下面是我如何成功解析一个字段：

use nom::bytes::complete::take_while1;
use nom::*;
use nom::character::is_alphabetic;

fn ident(c: char) -> bool {
    is_alphabetic(c as u8) || c == '_'
}

fn freetext(c: char) -> bool {
    c != '@'
}

fn parse_ident(s: &str) -> IResult<&str, &str> {
    take_while1(ident)(s)
}

fn parse_freetext(s: &str) -> IResult<&str, &str> {
    take_while1(freetext)(s)
}


named! {field_ident<&str, &str>,
    do_parse!(
        tag!("@") >>
        name: parse_ident >>
        (name)
    )
}

named! { field <&str, (&str, &str)>,
    do_parse!(
        name: ws!(field_ident) >>
        description: parse_freetext >>
        (name, description)
    )
}

当我将它包装到many1中并提供前面所述的输入时，我收到了Err(Incomplete(Size(1)))，但如果我在输入的末尾放入@，它就可以工作。如何在输入结束时将其标记为已完成？

Answer 1

您需要的是many_till组合器，而不是many1，如下所示：

use nom::bytes::complete::take_while1;
use nom::character::is_alphabetic;
use nom::*;

fn ident(c: char) -> bool {
    is_alphabetic(c as u8) || c == '_'
}

fn freetext(c: char) -> bool {
    c != '@'
}

fn parse_ident(s: &str) -> IResult<&str, &str> {
    take_while1(ident)(s)
}

fn parse_freetext(s: &str) -> IResult<&str, &str> {
    take_while1(freetext)(s)
}

named! {field_ident<&str, &str>,
    do_parse!(
        tag!("@") >>
        name: parse_ident >>
        (name)
    )
}

named! { field <&str, (&str, &str)>,
    do_parse!(
        name: ws!(field_ident) >>
        description: parse_freetext >>
        (name, description)
    )
}

named!(fields<&str, (Vec<(&str, &str)>, &str)>, many_till!(field, eof!()));

fn main() {
    println!("{:?}", field("@pook Some free text"));
    println!(
        "{:?}",
        fields("@pook Some free text @another_pook And another text")
    );
}

这是违反直觉的。我想，这与nom的流媒体特性有关。