24cc90262b
In particular, uses of inclusive ranges within the standard library are still waiting. Slices and collections can be sliced with `usize` and `Range*<usize>`, but not yet `Range*Inclusive<usize>`. Also, we need to figure out what to do about `RangeArgument`. Currently it has `start()` and `end()` methods which are pretty much identical to `Range::start` and `Range::end`. For the same reason as Range itself, these methods can't express a range such as `0...255u8` without overflow. The easiest choice, it seems to me, is either changing the meaning of `end()` to be inclusive, or adding a new method, say `last()`, that is inclusive and specifying that `end()` returns `None` in cases where it would overflow. Changing the semantics would be a breaking change, but `RangeArgument` is unstable so maybe we should do it anyway.
61 lines
1.6 KiB
Rust
61 lines
1.6 KiB
Rust
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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#![unstable(feature = "collections_range",
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reason = "waiting for dust to settle on inclusive ranges",
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issue = "30877")]
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//! Range syntax.
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use core::option::Option::{self, None, Some};
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use core::ops::{RangeFull, Range, RangeTo, RangeFrom};
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/// **RangeArgument** is implemented by Rust's built-in range types, produced
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/// by range syntax like `..`, `a..`, `..b` or `c..d`.
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pub trait RangeArgument<T> {
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/// Start index (inclusive)
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///
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/// Return start value if present, else `None`.
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fn start(&self) -> Option<&T> {
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None
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}
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/// End index (exclusive)
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///
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/// Return end value if present, else `None`.
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fn end(&self) -> Option<&T> {
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None
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}
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}
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// FIXME add inclusive ranges to RangeArgument
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impl<T> RangeArgument<T> for RangeFull {}
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impl<T> RangeArgument<T> for RangeFrom<T> {
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fn start(&self) -> Option<&T> {
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Some(&self.start)
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}
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}
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impl<T> RangeArgument<T> for RangeTo<T> {
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fn end(&self) -> Option<&T> {
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Some(&self.end)
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}
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}
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impl<T> RangeArgument<T> for Range<T> {
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fn start(&self) -> Option<&T> {
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Some(&self.start)
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}
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fn end(&self) -> Option<&T> {
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Some(&self.end)
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}
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}
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