Add initial impl of is_sorted to Iterator

This commit is contained in:
Kevin Leimkuhler 2018-10-11 09:53:15 -07:00
parent daa53a52a2
commit 8dea0d0172
6 changed files with 134 additions and 0 deletions

View File

@ -2605,6 +2605,90 @@ pub trait Iterator {
} }
} }
} }
/// Checks if the elements of this iterator are sorted.
///
/// That is, for each element `a` and its following element `b`, `a <= b`
/// must hold. If the iterator yields exactly zero or one element, `true`
/// is returned.
///
/// Note that if `Self::Item` is only `PartialOrd`, but not `Ord`, the above
/// definition implies that this function returns `false` if any two
/// consecutive items are not comparable.
///
/// # Examples
///
/// ```
/// #![feature(is_sorted)]
///
/// assert!([1, 2, 2, 9].iter().is_sorted());
/// assert!(![1, 3, 2, 4].iter().is_sorted());
/// assert!([0].iter().is_sorted());
/// assert!(std::iter::empty::<i32>().is_sorted());
/// assert!(![0.0, 1.0, std::f32::NAN].iter().is_sorted());
/// ```
#[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]
fn is_sorted(self) -> bool
where
Self: Sized,
Self::Item: PartialOrd,
{
self.is_sorted_by(|a, b| a.partial_cmp(b))
}
/// Checks if the elements of this iterator are sorted using the given
/// comparator function.
///
/// Instead of using `PartialOrd::partial_cmp`, this function uses the given
/// `compare` function to determine the ordering of two elements. Apart from
/// that, it's equivalent to `is_sorted`; see its documentation for more
/// information.
#[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]
fn is_sorted_by<F>(mut self, mut compare: F) -> bool
where
Self: Sized,
F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>
{
let mut last = match self.next() {
Some(e) => e,
None => return true,
};
while let Some(curr) = self.next() {
if compare(&last, &curr).map(|o| o == Ordering::Greater).unwrap_or(true) {
return false;
}
last = curr;
}
true
}
/// Checks if the elements of this iterator are sorted using the given
/// key extraction function.
///
/// Instead of comparing the iterator's elements directly, this function
/// compares the keys of the elements, as determined by `f`. Apart from
/// that, it's equivalent to `is_sorted`; see its documentation for more
/// information.
///
/// # Examples
///
/// ```
/// #![feature(is_sorted)]
///
/// assert!(["c", "bb", "aaa"].iter().is_sorted_by_key(|s| s.len()));
/// assert!(![-2i32, -1, 0, 3].iter().is_sorted_by_key(|n| n.abs()));
/// ```
#[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]
fn is_sorted_by_key<F, K>(self, mut f: F) -> bool
where
Self: Sized,
F: FnMut(&Self::Item) -> K,
K: PartialOrd
{
self.is_sorted_by(|a, b| f(a).partial_cmp(&f(b)))
}
} }
/// Select an element from an iterator based on the given "projection" /// Select an element from an iterator based on the given "projection"

View File

@ -79,6 +79,7 @@
#![feature(extern_types)] #![feature(extern_types)]
#![feature(fundamental)] #![feature(fundamental)]
#![feature(intrinsics)] #![feature(intrinsics)]
#![feature(is_sorted)]
#![feature(iter_once_with)] #![feature(iter_once_with)]
#![feature(lang_items)] #![feature(lang_items)]
#![feature(link_llvm_intrinsics)] #![feature(link_llvm_intrinsics)]

View File

@ -2235,3 +2235,16 @@ fn test_monad_laws_associativity() {
assert_eq!((0..10).flat_map(f).flat_map(g).sum::<usize>(), assert_eq!((0..10).flat_map(f).flat_map(g).sum::<usize>(),
(0..10).flat_map(|x| f(x).flat_map(g)).sum::<usize>()); (0..10).flat_map(|x| f(x).flat_map(g)).sum::<usize>());
} }
#[test]
fn test_is_sorted() {
assert!([1, 2, 2, 9].iter().is_sorted());
assert!(![1, 3, 2].iter().is_sorted());
assert!([0].iter().is_sorted());
assert!(std::iter::empty::<i32>().is_sorted());
assert!(![0.0, 1.0, std::f32::NAN].iter().is_sorted());
assert!([-2, -1, 0, 3].iter().is_sorted());
assert!(![-2i32, -1, 0, 3].iter().is_sorted_by_key(|n| n.abs()));
assert!(!["c", "bb", "aaa"].iter().is_sorted());
assert!(["c", "bb", "aaa"].iter().is_sorted_by_key(|s| s.len()));
}

View File

@ -10,6 +10,7 @@
#![feature(flt2dec)] #![feature(flt2dec)]
#![feature(fmt_internals)] #![feature(fmt_internals)]
#![feature(hashmap_internals)] #![feature(hashmap_internals)]
#![feature(is_sorted)]
#![feature(iter_copied)] #![feature(iter_copied)]
#![feature(iter_nth_back)] #![feature(iter_nth_back)]
#![feature(iter_once_with)] #![feature(iter_once_with)]

View File

@ -0,0 +1,16 @@
// Copyright 2018 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.
fn main() {
assert!([1, 2, 2, 9].iter().is_sorted());
//^ ERROR: use of unstable library feature 'is_sorted'
assert!(![-2i32, -1, 0, 3].iter().is_sorted_by_key(|n| n.abs()));
//^ ERROR: use of unstable library feature 'is_sorted'
}

View File

@ -0,0 +1,19 @@
error[E0658]: use of unstable library feature 'is_sorted': new API (see issue #53485)
--> $DIR/feature-gate-is_sorted.rs:12:33
|
LL | assert!([1, 2, 2, 9].iter().is_sorted());
| ^^^^^^^^^
|
= help: add #![feature(is_sorted)] to the crate attributes to enable
error[E0658]: use of unstable library feature 'is_sorted': new API (see issue #53485)
--> $DIR/feature-gate-is_sorted.rs:14:39
|
LL | assert!(![-2i32, -1, 0, 3].iter().is_sorted_by_key(|n| n.abs()));
| ^^^^^^^^^^^^^^^^
|
= help: add #![feature(is_sorted)] to the crate attributes to enable
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0658`.