rust/src/libcore/ops/range.rs

// Copyright 2012 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 fmt;
use ops::Bound::{Included, Excluded, Unbounded};

/// An unbounded range. Use `..` (two dots) for its shorthand.
///
/// Its primary use case is slicing index. It cannot serve as an iterator
/// because it doesn't have a starting point.
///
/// # Examples
///
/// The `..` syntax is a `RangeFull`:
///
/// ```
/// assert_eq!((..), std::ops::RangeFull);
/// ```
///
/// It does not have an `IntoIterator` implementation, so you can't use it in a
/// `for` loop directly. This won't compile:
///
/// ```compile_fail,E0277
/// for i in .. {
///    // ...
/// }
/// ```
///
/// Used as a slicing index, `RangeFull` produces the full array as a slice.
///
/// ```
/// let arr = [0, 1, 2, 3];
/// assert_eq!(arr[ .. ], [0,1,2,3]);  // RangeFull
/// assert_eq!(arr[ ..3], [0,1,2  ]);
/// assert_eq!(arr[1.. ], [  1,2,3]);
/// assert_eq!(arr[1..3], [  1,2  ]);
/// ```
#[derive(Copy, Clone, PartialEq, Eq, Hash)]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct RangeFull;

#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Debug for RangeFull {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        write!(fmt, "..")
    }
}

/// A (half-open) range which is bounded at both ends: { x | start <= x < end }.
/// Use `start..end` (two dots) for its shorthand.
///
/// See the [`contains`](#method.contains) method for its characterization.
///
/// # Examples
///
/// ```
/// fn main() {
///     assert_eq!((3..5), std::ops::Range{ start: 3, end: 5 });
///     assert_eq!(3+4+5, (3..6).sum());
///
///     let arr = [0, 1, 2, 3];
///     assert_eq!(arr[ .. ], [0,1,2,3]);
///     assert_eq!(arr[ ..3], [0,1,2  ]);
///     assert_eq!(arr[1.. ], [  1,2,3]);
///     assert_eq!(arr[1..3], [  1,2  ]);  // Range
/// }
/// ```
#[derive(Clone, PartialEq, Eq, Hash)]
// not Copy -- see #27186
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Range<Idx> {
    /// The lower bound of the range (inclusive).
    #[stable(feature = "rust1", since = "1.0.0")]
    pub start: Idx,
    /// The upper bound of the range (exclusive).
    #[stable(feature = "rust1", since = "1.0.0")]
    pub end: Idx,
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<Idx: fmt::Debug> fmt::Debug for Range<Idx> {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        write!(fmt, "{:?}..{:?}", self.start, self.end)
    }
}

#[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
impl<Idx: PartialOrd<Idx>> Range<Idx> {
    /// # Examples
    ///
    /// ```
    /// #![feature(range_contains)]
    /// fn main() {
    ///     assert!( ! (3..5).contains(2));
    ///     assert!(   (3..5).contains(3));
    ///     assert!(   (3..5).contains(4));
    ///     assert!( ! (3..5).contains(5));
    ///
    ///     assert!( ! (3..3).contains(3));
    ///     assert!( ! (3..2).contains(3));
    /// }
    /// ```
    pub fn contains(&self, item: Idx) -> bool {
        (self.start <= item) && (item < self.end)
    }
}

/// A range which is only bounded below: { x | start <= x }.
/// Use `start..` for its shorthand.
///
/// See the [`contains`](#method.contains) method for its characterization.
///
/// Note: Currently, no overflow checking is done for the iterator
/// implementation; if you use an integer range and the integer overflows, it
/// might panic in debug mode or create an endless loop in release mode. This
/// overflow behavior might change in the future.
///
/// # Examples
///
/// ```
/// fn main() {
///     assert_eq!((2..), std::ops::RangeFrom{ start: 2 });
///     assert_eq!(2+3+4, (2..).take(3).sum());
///
///     let arr = [0, 1, 2, 3];
///     assert_eq!(arr[ .. ], [0,1,2,3]);
///     assert_eq!(arr[ ..3], [0,1,2  ]);
///     assert_eq!(arr[1.. ], [  1,2,3]);  // RangeFrom
///     assert_eq!(arr[1..3], [  1,2  ]);
/// }
/// ```
#[derive(Clone, PartialEq, Eq, Hash)]
// not Copy -- see #27186
#[stable(feature = "rust1", since = "1.0.0")]
pub struct RangeFrom<Idx> {
    /// The lower bound of the range (inclusive).
    #[stable(feature = "rust1", since = "1.0.0")]
    pub start: Idx,
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<Idx: fmt::Debug> fmt::Debug for RangeFrom<Idx> {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        write!(fmt, "{:?}..", self.start)
    }
}

#[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
impl<Idx: PartialOrd<Idx>> RangeFrom<Idx> {
    /// # Examples
    ///
    /// ```
    /// #![feature(range_contains)]
    /// fn main() {
    ///     assert!( ! (3..).contains(2));
    ///     assert!(   (3..).contains(3));
    ///     assert!(   (3..).contains(1_000_000_000));
    /// }
    /// ```
    pub fn contains(&self, item: Idx) -> bool {
        (self.start <= item)
    }
}

/// A range which is only bounded above: { x | x < end }.
/// Use `..end` (two dots) for its shorthand.
///
/// See the [`contains`](#method.contains) method for its characterization.
///
/// It cannot serve as an iterator because it doesn't have a starting point.
///
/// # Examples
///
/// The `..{integer}` syntax is a `RangeTo`:
///
/// ```
/// assert_eq!((..5), std::ops::RangeTo{ end: 5 });
/// ```
///
/// It does not have an `IntoIterator` implementation, so you can't use it in a
/// `for` loop directly. This won't compile:
///
/// ```compile_fail,E0277
/// for i in ..5 {
///     // ...
/// }
/// ```
///
/// When used as a slicing index, `RangeTo` produces a slice of all array
/// elements before the index indicated by `end`.
///
/// ```
/// let arr = [0, 1, 2, 3];
/// assert_eq!(arr[ .. ], [0,1,2,3]);
/// assert_eq!(arr[ ..3], [0,1,2  ]);  // RangeTo
/// assert_eq!(arr[1.. ], [  1,2,3]);
/// assert_eq!(arr[1..3], [  1,2  ]);
/// ```
#[derive(Copy, Clone, PartialEq, Eq, Hash)]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct RangeTo<Idx> {
    /// The upper bound of the range (exclusive).
    #[stable(feature = "rust1", since = "1.0.0")]
    pub end: Idx,
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<Idx: fmt::Debug> fmt::Debug for RangeTo<Idx> {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        write!(fmt, "..{:?}", self.end)
    }
}

#[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
impl<Idx: PartialOrd<Idx>> RangeTo<Idx> {
    /// # Examples
    ///
    /// ```
    /// #![feature(range_contains)]
    /// fn main() {
    ///     assert!(   (..5).contains(-1_000_000_000));
    ///     assert!(   (..5).contains(4));
    ///     assert!( ! (..5).contains(5));
    /// }
    /// ```
    pub fn contains(&self, item: Idx) -> bool {
        (item < self.end)
    }
}

/// An inclusive range which is bounded at both ends: { x | start <= x <= end }.
/// Use `start...end` (three dots) for its shorthand.
///
/// See the [`contains`](#method.contains) method for its characterization.
///
/// # Examples
///
/// ```
/// #![feature(inclusive_range,inclusive_range_syntax)]
/// fn main() {
///     assert_eq!((3...5), std::ops::RangeInclusive{ start: 3, end: 5 });
///     assert_eq!(3+4+5, (3...5).sum());
///
///     let arr = [0, 1, 2, 3];
///     assert_eq!(arr[ ...2], [0,1,2  ]);
///     assert_eq!(arr[1...2], [  1,2  ]);  // RangeInclusive
/// }
/// ```
#[derive(Clone, PartialEq, Eq, Hash)]
// not Copy -- see #27186
#[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
pub struct RangeInclusive<Idx> {
    /// The lower bound of the range (inclusive).
    #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC",
               issue = "28237")]
    pub start: Idx,
    /// The upper bound of the range (inclusive).
    #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC",
               issue = "28237")]
    pub end: Idx,
}

#[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
impl<Idx: fmt::Debug> fmt::Debug for RangeInclusive<Idx> {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        write!(fmt, "{:?}...{:?}", self.start, self.end)
    }
}

#[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
impl<Idx: PartialOrd<Idx>> RangeInclusive<Idx> {
    /// # Examples
    ///
    /// ```
    /// #![feature(range_contains,inclusive_range_syntax)]
    /// fn main() {
    ///     assert!( ! (3...5).contains(2));
    ///     assert!(   (3...5).contains(3));
    ///     assert!(   (3...5).contains(4));
    ///     assert!(   (3...5).contains(5));
    ///     assert!( ! (3...5).contains(6));
    ///
    ///     assert!(   (3...3).contains(3));
    ///     assert!( ! (3...2).contains(3));
    /// }
    /// ```
    pub fn contains(&self, item: Idx) -> bool {
        self.start <= item && item <= self.end
    }
}

/// An inclusive range which is only bounded above: { x | x <= end }.
/// Use `...end` (three dots) for its shorthand.
///
/// See the [`contains`](#method.contains) method for its characterization.
///
/// It cannot serve as an iterator because it doesn't have a starting point.
///
/// # Examples
///
/// The `...{integer}` syntax is a `RangeToInclusive`:
///
/// ```
/// #![feature(inclusive_range,inclusive_range_syntax)]
/// assert_eq!((...5), std::ops::RangeToInclusive{ end: 5 });
/// ```
///
/// It does not have an `IntoIterator` implementation, so you can't use it in a
/// `for` loop directly. This won't compile:
///
/// ```compile_fail,E0277
/// #![feature(inclusive_range_syntax)]
/// for i in ...5 {
///     // ...
/// }
/// ```
///
/// When used as a slicing index, `RangeToInclusive` produces a slice of all
/// array elements up to and including the index indicated by `end`.
///
/// ```
/// #![feature(inclusive_range_syntax)]
/// let arr = [0, 1, 2, 3];
/// assert_eq!(arr[ ...2], [0,1,2  ]);  // RangeToInclusive
/// assert_eq!(arr[1...2], [  1,2  ]);
/// ```
#[derive(Copy, Clone, PartialEq, Eq, Hash)]
#[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
pub struct RangeToInclusive<Idx> {
    /// The upper bound of the range (inclusive)
    #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC",
               issue = "28237")]
    pub end: Idx,
}

#[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
impl<Idx: fmt::Debug> fmt::Debug for RangeToInclusive<Idx> {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        write!(fmt, "...{:?}", self.end)
    }
}

#[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
impl<Idx: PartialOrd<Idx>> RangeToInclusive<Idx> {
    /// # Examples
    ///
    /// ```
    /// #![feature(range_contains,inclusive_range_syntax)]
    /// fn main() {
    ///     assert!(   (...5).contains(-1_000_000_000));
    ///     assert!(   (...5).contains(5));
    ///     assert!( ! (...5).contains(6));
    /// }
    /// ```
    pub fn contains(&self, item: Idx) -> bool {
        (item <= self.end)
    }
}

// RangeToInclusive<Idx> cannot impl From<RangeTo<Idx>>
// because underflow would be possible with (..0).into()

/// `RangeArgument` is implemented by Rust's built-in range types, produced
/// by range syntax like `..`, `a..`, `..b` or `c..d`.
#[stable(feature = "range_argument", since = "1.19.0")]
pub trait RangeArgument<T: ?Sized> {
    /// Start index bound.
    ///
    /// Returns the start value as a `Bound`.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::ops::RangeArgument;
    /// use std::ops::Bound::*;
    ///
    /// assert_eq!((..10).start(), Unbounded);
    /// assert_eq!((3..10).start(), Included(&3));
    /// ```
    #[stable(feature = "range_argument", since = "1.19.0")]
    fn start(&self) -> Bound<&T>;

    /// End index bound.
    ///
    /// Returns the end value as a `Bound`.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::ops::RangeArgument;
    /// use std::ops::Bound::*;
    ///
    /// assert_eq!((3..).end(), Unbounded);
    /// assert_eq!((3..10).end(), Excluded(&10));
    /// ```
    #[stable(feature = "range_argument", since = "1.19.0")]
    fn end(&self) -> Bound<&T>;
}

#[stable(feature = "range_argument", since = "1.19.0")]
impl<T: ?Sized> RangeArgument<T> for RangeFull {
    fn start(&self) -> Bound<&T> {
        Unbounded
    }
    fn end(&self) -> Bound<&T> {
        Unbounded
    }
}

#[stable(feature = "range_argument", since = "1.19.0")]
impl<T> RangeArgument<T> for RangeFrom<T> {
    fn start(&self) -> Bound<&T> {
        Included(&self.start)
    }
    fn end(&self) -> Bound<&T> {
        Unbounded
    }
}

#[stable(feature = "range_argument", since = "1.19.0")]
impl<T> RangeArgument<T> for RangeTo<T> {
    fn start(&self) -> Bound<&T> {
        Unbounded
    }
    fn end(&self) -> Bound<&T> {
        Excluded(&self.end)
    }
}

#[stable(feature = "range_argument", since = "1.19.0")]
impl<T> RangeArgument<T> for Range<T> {
    fn start(&self) -> Bound<&T> {
        Included(&self.start)
    }
    fn end(&self) -> Bound<&T> {
        Excluded(&self.end)
    }
}

#[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
impl<T> RangeArgument<T> for RangeInclusive<T> {
    fn start(&self) -> Bound<&T> {
        Included(&self.start)
    }
    fn end(&self) -> Bound<&T> {
        Included(&self.end)
    }
}

#[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
impl<T> RangeArgument<T> for RangeToInclusive<T> {
    fn start(&self) -> Bound<&T> {
        Unbounded
    }
    fn end(&self) -> Bound<&T> {
        Included(&self.end)
    }
}

#[stable(feature = "range_argument", since = "1.19.0")]
impl<T> RangeArgument<T> for (Bound<T>, Bound<T>) {
    fn start(&self) -> Bound<&T> {
        match *self {
            (Included(ref start), _) => Included(start),
            (Excluded(ref start), _) => Excluded(start),
            (Unbounded, _) => Unbounded,
        }
    }

    fn end(&self) -> Bound<&T> {
        match *self {
            (_, Included(ref end)) => Included(end),
            (_, Excluded(ref end)) => Excluded(end),
            (_, Unbounded) => Unbounded,
        }
    }
}

#[stable(feature = "range_argument", since = "1.19.0")]
impl<'a, T: ?Sized + 'a> RangeArgument<T> for (Bound<&'a T>, Bound<&'a T>) {
    fn start(&self) -> Bound<&T> {
        self.0
    }

    fn end(&self) -> Bound<&T> {
        self.1
    }
}

/// An endpoint of a range of keys.
///
/// # Examples
///
/// `Bound`s are range endpoints:
///
/// ```
/// use std::ops::RangeArgument;
/// use std::ops::Bound::*;
///
/// assert_eq!((..100).start(), Unbounded);
/// assert_eq!((1..12).start(), Included(&1));
/// assert_eq!((1..12).end(), Excluded(&12));
/// ```
#[stable(feature = "collections_bound", since = "1.17.0")]
#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
pub enum Bound<T> {
    /// An inclusive bound.
    #[stable(feature = "collections_bound", since = "1.17.0")]
    Included(T),
    /// An exclusive bound.
    #[stable(feature = "collections_bound", since = "1.17.0")]
    Excluded(T),
    /// An infinite endpoint. Indicates that there is no bound in this direction.
    #[stable(feature = "collections_bound", since = "1.17.0")]
    Unbounded,
}