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    // Copyright 2014-2015 The Rust Project Developers. See the COPYRIGHT
    // file at the top-level directory of this distribution and at
    // http://rust-lang.org/COPYRIGHT.
    //
    // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
    // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
    // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
    // option. This file may not be copied, modified, or distributed
    // except according to those terms.

    use std::char;
    use std::cmp::Ordering;
    use std::fmt;
    use std::u32;

    use syntax;

    /// An inline representation of `Option<char>`.
    ///
    /// This eliminates the need to do case analysis on `Option<char>` to determine
    /// ordinality with other characters.
    ///
    /// (The `Option<char>` is not related to encoding. Instead, it is used in the
    /// matching engines to represent the beginning and ending boundaries of the
    /// search text.)
    #[derive(Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
    pub struct Char(u32);

    impl fmt::Debug for Char {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            match char::from_u32(self.0) {
                None => write!(f, "Empty"),
                Some(c) => write!(f, "{:?}", c),
            }
        }
    }

    impl Char {
        /// Returns true iff the character is absent.
        #[inline]
        pub fn is_none(self) -> bool { self.0 == u32::MAX }

        /// Returns the length of the character's UTF-8 encoding.
        ///
        /// If the character is absent, then `0` is returned.
        #[inline]
        pub fn len_utf8(self) -> usize {
            char::from_u32(self.0).map_or(0, |c| c.len_utf8())
        }

        /// Returns true iff the character is a word character.
        ///
        /// If the character is absent, then false is returned.
        pub fn is_word_char(self) -> bool {
            char::from_u32(self.0).map_or(false, syntax::is_word_char)
        }

        /// Converts the character to a real primitive `char`.
        ///
        /// If the character is absent, then `None` is returned.
        pub fn as_char(self) -> Option<char> {
            // This is only used in the `regex!` macro because it expands char
            // classes into `match` expressions (instead of binary search).
            char::from_u32(self.0)
        }
    }

    impl From<char> for Char {
        fn from(c: char) -> Char { Char(c as u32) }
    }

    impl From<Option<char>> for Char {
        fn from(c: Option<char>) -> Char {
            c.map_or(Char(u32::MAX), |c| c.into())
        }
    }

    impl PartialEq<char> for Char {
        #[inline]
        fn eq(&self, other: &char) -> bool { self.0 == *other as u32 }
    }

    impl PartialEq<Char> for char {
        #[inline]
        fn eq(&self, other: &Char) -> bool { *self as u32 == other.0 }
    }

    impl PartialOrd<char> for Char {
        #[inline]
        fn partial_cmp(&self, other: &char) -> Option<Ordering> {
            self.0.partial_cmp(&(*other as u32))
        }
    }

    impl PartialOrd<Char> for char {
        #[inline]
        fn partial_cmp(&self, other: &Char) -> Option<Ordering> {
            (*self as u32).partial_cmp(&other.0)
        }
    }

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