src/libcollections/range.rs

// Copyright 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.

#![unstable(feature = "collections_range", reason = "was just added")]

//! Range syntax.

use core::option::Option::{self, None, Some};
use core::ops::{RangeFull, Range, RangeTo, RangeFrom};

/// **RangeArgument** is implemented by Rust's built-in range types, produced
/// by range syntax like `..`, `a..`, `..b` or `c..d`.
pub trait RangeArgument<T> {
    /// Start index (inclusive)
    ///
    /// Return start value if present, else `None`.
    fn start(&self) -> Option<&T> { None }

    /// End index (exclusive)
    ///
    /// Return end value if present, else `None`.
    fn end(&self) -> Option<&T> { None }
}


impl<T> RangeArgument<T> for RangeFull {}

impl<T> RangeArgument<T> for RangeFrom<T> {
    fn start(&self) -> Option<&T> { Some(&self.start) }
}

impl<T> RangeArgument<T> for RangeTo<T> {
    fn end(&self) -> Option<&T> { Some(&self.end) }
}

impl<T> RangeArgument<T> for Range<T> {
    fn start(&self) -> Option<&T> { Some(&self.start) }
    fn end(&self) -> Option<&T> { Some(&self.end) }
}