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/Rust

Trait RangeBounds

pub trait RangeBounds<T>where
    T: ?Sized,{
    // Required methods
    fn start_bound(&self) -> Bound<&T>;
    fn end_bound(&self) -> Bound<&T>;

    // Provided methods
    fn contains<U>(&self, item: &U) -> bool
       where T: PartialOrd<U>,
             U: PartialOrd<T> + ?Sized { ... }
    fn is_empty(&self) -> bool
       where T: PartialOrd { ... }
}

🔬This is a nightly-only experimental API. (new_range_api #125687)

RangeBounds is implemented by Rust’s built-in range types, produced by range syntax like .., a.., ..b, ..=c, d..e, or f..=g.

Required Methods

1.28.0Source

fn start_bound(&self) -> Bound<&T>

Start index bound.

Returns the start value as a Bound.

Examples

use std::ops::Bound::*;
use std::ops::RangeBounds;

assert_eq!((..10).start_bound(), Unbounded);
assert_eq!((3..10).start_bound(), Included(&3));

1.28.0Source

fn end_bound(&self) -> Bound<&T>

End index bound.

Returns the end value as a Bound.

Examples

use std::ops::Bound::*;
use std::ops::RangeBounds;

assert_eq!((3..).end_bound(), Unbounded);
assert_eq!((3..10).end_bound(), Excluded(&10));

Provided Methods

1.35.0Source

fn contains<U>(&self, item: &U) -> boolwhere
    T: PartialOrd<U>,
    U: PartialOrd<T> + ?Sized,

Returns true if item is contained in the range.

Examples

assert!( (3..5).contains(&4));
assert!(!(3..5).contains(&2));

assert!( (0.0..1.0).contains(&0.5));
assert!(!(0.0..1.0).contains(&f32::NAN));
assert!(!(0.0..f32::NAN).contains(&0.5));
assert!(!(f32::NAN..1.0).contains(&0.5));

Source

fn is_empty(&self) -> boolwhere
    T: PartialOrd,

🔬This is a nightly-only experimental API. (range_bounds_is_empty #137300)

Returns true if the range contains no items. One-sided ranges (RangeFrom, etc) always return false.

Examples

#![feature(range_bounds_is_empty)]
use std::ops::RangeBounds;

assert!(!(3..).is_empty());
assert!(!(..2).is_empty());
assert!(!RangeBounds::is_empty(&(3..5)));
assert!( RangeBounds::is_empty(&(3..3)));
assert!( RangeBounds::is_empty(&(3..2)));

The range is empty if either side is incomparable:

#![feature(range_bounds_is_empty)]
use std::ops::RangeBounds;

assert!(!RangeBounds::is_empty(&(3.0..5.0)));
assert!( RangeBounds::is_empty(&(3.0..f32::NAN)));
assert!( RangeBounds::is_empty(&(f32::NAN..5.0)));

But never empty if either side is unbounded:

#![feature(range_bounds_is_empty)]
use std::ops::RangeBounds;

assert!(!(..0).is_empty());
assert!(!(i32::MAX..).is_empty());
assert!(!RangeBounds::<u8>::is_empty(&(..)));

(Excluded(a), Excluded(b)) is only empty if a >= b:

#![feature(range_bounds_is_empty)]
use std::ops::Bound::*;
use std::ops::RangeBounds;

assert!(!(Excluded(1), Excluded(3)).is_empty());
assert!(!(Excluded(1), Excluded(2)).is_empty());
assert!( (Excluded(1), Excluded(1)).is_empty());
assert!( (Excluded(2), Excluded(1)).is_empty());
assert!( (Excluded(3), Excluded(1)).is_empty());

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.