nomnom.rs

#[macro_use]
extern crate nom;

use nom::{IResult, is_digit};
use std::str;

#[derive(Debug, PartialEq, Eq)]
pub enum Sign {
    Plus,
    Minus,
}

named!(pub sign<Sign>, map!(
    alt!(tag!(b"+") | tag!(b"-")),
    |x| if x == b"+" { Sign::Plus } else { Sign::Minus }
  )
);

type DigitSequence<'a> = &'a[u8];
named!(pub digit_sequence<DigitSequence>, take_while1!(is_digit));

type Exponent<'a> = (Sign, &'a[u8]);
named!(pub exponent<Exponent>, do_parse!(
    alt!(tag!(b"e") | tag!(b"E")) >>
    s: opt!(sign)                 >>
    d: digit_sequence             >>
    (s.unwrap_or(Sign::Plus), d)
));

type FractionalConstant<'a> = (Option<&'a[u8]>, Option<&'a[u8]>);
named!(pub fractional_constant<FractionalConstant>, alt!(
    do_parse!(
        i: opt!(digit_sequence) >>
           tag!(b".")           >>
        f: digit_sequence       >>
        (i, Some(f))
    ) |
    do_parse!(
        i: digit_sequence       >>
           tag!(b".")           >>
        (Some(i), None)
    )
));

type FloatingPointConstant<'a> = (FractionalConstant<'a>, Option<Exponent<'a>>);
named!(pub floating_point_constant<FloatingPointConstant>, alt!(
    do_parse!(
        f: fractional_constant >>
        e: opt!(exponent)      >>
        (f, e)
    ) |
    do_parse!(
        d: digit_sequence      >>
        e: exponent            >>
        ((Some(d), None), Some(e))
    )
));

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn it_works() {
        assert_eq!(sign(b"+"), IResult::Done(&b""[..], Sign::Plus));
        assert_eq!(sign(b"-"), IResult::Done(&b""[..], Sign::Minus));
        assert_eq!(digit_sequence(b"123456"), IResult::Done(&b""[..], &b"123456"[..]));
        assert_eq!(digit_sequence(b"123456b"), IResult::Done(&b"b"[..], &b"123456"[..]));
        assert_eq!(digit_sequence(b"1234b56"), IResult::Done(&b"b56"[..], &b"1234"[..]));
        assert_eq!(exponent(b"e123"), IResult::Done(&b""[..], (Sign::Plus, &b"123"[..])));
        assert_eq!(exponent(b"e+123"), IResult::Done(&b""[..], (Sign::Plus, &b"123"[..])));
        assert_eq!(exponent(b"e-123"), IResult::Done(&b""[..], (Sign::Minus, &b"123"[..])));
        assert_eq!(fractional_constant(b"1.23"), IResult::Done(&b""[..], (Some(&b"1"[..]), Some(&b"23"[..]))));
        assert_eq!(fractional_constant(b"1."), IResult::Done(&b""[..], (Some(&b"1"[..]), None)));
        assert_eq!(fractional_constant(b".23"), IResult::Done(&b""[..], (None, Some(&b"23"[..]))));

    }
}