p-arse 0.0.1

the inelegant parser
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//! String slices and characters.

use crate::{Error, Parser, Result};

impl<'b> Parser for &'b str {
    type Output = &'b str;

    fn p_arse<'a>(&self, tail: &'a str) -> Result<'a, Self::Output> {
        let stripped = tail.strip_prefix(self).ok_or_else(|| {
            Error::expecting(format!("string '{}'", self), tail)
        })?;

        Ok((self, stripped))
    }
}

impl Parser for char {
    type Output = char;

    fn p_arse<'a>(&self, tail: &'a str) -> Result<'a, Self::Output> {
        let mut chars = tail.chars();
        let first = chars.next().ok_or_else(|| {
            Error::expecting(format!("char '{}'", self), tail)
        })?;

        if first == *self {
            let tail = chars.as_str();

            Ok((first, tail))
        } else {
            Err(Error::expecting(format!("char '{}'", self), tail))
        }
    }
}

/// A [`Copy`] [`char`] range.
#[derive(Copy, Clone)]
pub struct CharRange {
    from: char,
    to: char,
}

/// Trait enabling a concise syntax for construction of [`CharRange`].
///
/// # Examples
///
/// ```
/// use p_arse::CharExt;
///
/// let a_to_z = 'a'.to('z');
/// ```
pub trait CharExt {
    fn to(self, to: char) -> CharRange;
}

impl CharExt for char {
    fn to(self, to: char) -> CharRange {
        CharRange { from: self, to }
    }
}

impl Parser for CharRange {
    type Output = char;

    fn p_arse<'a>(&self, tail: &'a str) -> Result<'a, Self::Output> {
        let mut chars = tail.chars();
        let first = chars.next().ok_or_else(|| {
            Error::expecting(
                format!("char from '{}' to '{}'", self.from, self.to),
                tail,
            )
        })?;

        if (self.from..=self.to).contains(&first) {
            let tail = chars.as_str();

            Ok((first, tail))
        } else {
            Err(Error::expecting(
                format!("char from '{}' to '{}'", self.from, self.to),
                tail,
            ))
        }
    }
}