1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
// 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;

/// An unbounded range (`..`).
///
/// `RangeFull` is primarily used as a [slicing index], its shorthand is `..`.
/// 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  ]);
/// ```
///
/// [`IntoIterator`]: ../iter/trait.Iterator.html
/// [`Iterator`]: ../iter/trait.IntoIterator.html
/// [slicing index]: ../slice/trait.SliceIndex.html
#[doc(alias = "..")]
#[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 bounded inclusively below and exclusively above
/// (`start..end`).
///
/// The `Range` `start..end` contains all values with `x >= start` and
/// `x < end`.  It is empty unless `start < end`.
///
/// # Examples
///
/// ```
/// assert_eq!((3..5), std::ops::Range { start: 3, end: 5 });
/// assert_eq!(3 + 4 + 5, (3..6).sum());
///
/// let arr = ['a', 'b', 'c', 'd'];
/// assert_eq!(arr[ .. ], ['a', 'b', 'c', 'd']);
/// assert_eq!(arr[ ..3], ['a', 'b', 'c',    ]);
/// assert_eq!(arr[1.. ], [     'b', 'c', 'd']);
/// assert_eq!(arr[1..3], [     'b', 'c'     ]);  // Range
/// ```
#[doc(alias = "..")]
#[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)
    }
}

impl<Idx: PartialOrd<Idx>> Range<Idx> {
    /// Returns `true` if `item` is contained in the range.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(range_contains)]
    ///
    /// use std::f32;
    ///
    /// 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));
    ///
    /// 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));
    /// ```
    #[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
    pub fn contains<U>(&self, item: &U) -> bool
    where
        Idx: PartialOrd<U>,
        U: ?Sized + PartialOrd<Idx>,
    {
        <Self as RangeBounds<Idx>>::contains(self, item)
    }

    /// Returns `true` if the range contains no items.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(range_is_empty)]
    ///
    /// assert!(!(3..5).is_empty());
    /// assert!( (3..3).is_empty());
    /// assert!( (3..2).is_empty());
    /// ```
    ///
    /// The range is empty if either side is incomparable:
    ///
    /// ```
    /// #![feature(range_is_empty)]
    ///
    /// use std::f32::NAN;
    /// assert!(!(3.0..5.0).is_empty());
    /// assert!( (3.0..NAN).is_empty());
    /// assert!( (NAN..5.0).is_empty());
    /// ```
    #[unstable(feature = "range_is_empty", reason = "recently added", issue = "48111")]
    pub fn is_empty(&self) -> bool {
        !(self.start < self.end)
    }
}

/// A range only bounded inclusively below (`start..`).
///
/// The `RangeFrom` `start..` contains all values with `x >= start`.
///
/// *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
///
/// ```
/// 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  ]);
/// ```
///
/// [`Iterator`]: ../iter/trait.IntoIterator.html
#[doc(alias = "..")]
#[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)
    }
}

impl<Idx: PartialOrd<Idx>> RangeFrom<Idx> {
    /// Returns `true` if `item` is contained in the range.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(range_contains)]
    ///
    /// use std::f32;
    ///
    /// assert!(!(3..).contains(&2));
    /// assert!( (3..).contains(&3));
    /// assert!( (3..).contains(&1_000_000_000));
    ///
    /// assert!( (0.0..).contains(&0.5));
    /// assert!(!(0.0..).contains(&f32::NAN));
    /// assert!(!(f32::NAN..).contains(&0.5));
    /// ```
    #[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
    pub fn contains<U>(&self, item: &U) -> bool
    where
        Idx: PartialOrd<U>,
        U: ?Sized + PartialOrd<Idx>,
    {
        <Self as RangeBounds<Idx>>::contains(self, item)
    }
}

/// A range only bounded exclusively above (`..end`).
///
/// The `RangeTo` `..end` contains all values with `x < end`.
/// It cannot serve as an [`Iterator`] because it doesn't have a starting point.
///
/// # Examples
///
/// The `..end` 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
/// // error[E0277]: the trait bound `std::ops::RangeTo<{integer}>:
/// // std::iter::Iterator` is not satisfied
/// 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  ]);
/// ```
///
/// [`IntoIterator`]: ../iter/trait.Iterator.html
/// [`Iterator`]: ../iter/trait.IntoIterator.html
/// [slicing index]: ../slice/trait.SliceIndex.html
#[doc(alias = "..")]
#[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)
    }
}

impl<Idx: PartialOrd<Idx>> RangeTo<Idx> {
    /// Returns `true` if `item` is contained in the range.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(range_contains)]
    ///
    /// use std::f32;
    ///
    /// assert!( (..5).contains(&-1_000_000_000));
    /// assert!( (..5).contains(&4));
    /// assert!(!(..5).contains(&5));
    ///
    /// assert!( (..1.0).contains(&0.5));
    /// assert!(!(..1.0).contains(&f32::NAN));
    /// assert!(!(..f32::NAN).contains(&0.5));
    /// ```
    #[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
    pub fn contains<U>(&self, item: &U) -> bool
    where
        Idx: PartialOrd<U>,
        U: ?Sized + PartialOrd<Idx>,
    {
        <Self as RangeBounds<Idx>>::contains(self, item)
    }
}

/// An range bounded inclusively below and above (`start..=end`).
///
/// The `RangeInclusive` `start..=end` contains all values with `x >= start`
/// and `x <= end`.  It is empty unless `start <= end`.
///
/// This iterator is [fused], but the specific values of `start` and `end` after
/// iteration has finished are **unspecified** other than that [`.is_empty()`]
/// will return `true` once no more values will be produced.
///
/// [fused]: ../iter/trait.FusedIterator.html
/// [`.is_empty()`]: #method.is_empty
///
/// # Examples
///
/// ```
/// assert_eq!((3..=5), std::ops::RangeInclusive::new(3, 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
/// ```
#[doc(alias = "..=")]
#[derive(Clone, PartialEq, Eq, Hash)]  // not Copy -- see #27186
#[stable(feature = "inclusive_range", since = "1.26.0")]
pub struct RangeInclusive<Idx> {
    // FIXME: The current representation follows RFC 1980,
    // but it is known that LLVM is not able to optimize loops following that RFC.
    // Consider adding an extra `bool` field to indicate emptiness of the range.
    // See #45222 for performance test cases.
    #[cfg(not(stage0))]
    pub(crate) start: Idx,
    #[cfg(not(stage0))]
    pub(crate) end: Idx,
    /// The lower bound of the range (inclusive).
    #[cfg(stage0)]
    #[unstable(feature = "inclusive_range_fields", issue = "49022")]
    pub start: Idx,
    /// The upper bound of the range (inclusive).
    #[cfg(stage0)]
    #[unstable(feature = "inclusive_range_fields", issue = "49022")]
    pub end: Idx,
}

impl<Idx> RangeInclusive<Idx> {
    /// Creates a new inclusive range. Equivalent to writing `start..=end`.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::ops::RangeInclusive;
    ///
    /// assert_eq!(3..=5, RangeInclusive::new(3, 5));
    /// ```
    #[stable(feature = "inclusive_range_methods", since = "1.27.0")]
    #[inline]
    pub const fn new(start: Idx, end: Idx) -> Self {
        Self { start, end }
    }

    /// Returns the lower bound of the range (inclusive).
    ///
    /// When using an inclusive range for iteration, the values of `start()` and
    /// [`end()`] are unspecified after the iteration ended. To determine
    /// whether the inclusive range is empty, use the [`is_empty()`] method
    /// instead of comparing `start() > end()`.
    ///
    /// Note: the value returned by this method is unspecified after the range
    /// has been iterated to exhaustion.
    ///
    /// [`end()`]: #method.end
    /// [`is_empty()`]: #method.is_empty
    ///
    /// # Examples
    ///
    /// ```
    /// assert_eq!((3..=5).start(), &3);
    /// ```
    #[stable(feature = "inclusive_range_methods", since = "1.27.0")]
    #[inline]
    pub fn start(&self) -> &Idx {
        &self.start
    }

    /// Returns the upper bound of the range (inclusive).
    ///
    /// When using an inclusive range for iteration, the values of [`start()`]
    /// and `end()` are unspecified after the iteration ended. To determine
    /// whether the inclusive range is empty, use the [`is_empty()`] method
    /// instead of comparing `start() > end()`.
    ///
    /// Note: the value returned by this method is unspecified after the range
    /// has been iterated to exhaustion.
    ///
    /// [`start()`]: #method.start
    /// [`is_empty()`]: #method.is_empty
    ///
    /// # Examples
    ///
    /// ```
    /// assert_eq!((3..=5).end(), &5);
    /// ```
    #[stable(feature = "inclusive_range_methods", since = "1.27.0")]
    #[inline]
    pub fn end(&self) -> &Idx {
        &self.end
    }

    /// Destructures the `RangeInclusive` into (lower bound, upper (inclusive) bound).
    ///
    /// Note: the value returned by this method is unspecified after the range
    /// has been iterated to exhaustion.
    ///
    /// # Examples
    ///
    /// ```
    /// assert_eq!((3..=5).into_inner(), (3, 5));
    /// ```
    #[stable(feature = "inclusive_range_methods", since = "1.27.0")]
    #[inline]
    pub fn into_inner(self) -> (Idx, Idx) {
        (self.start, self.end)
    }
}

#[stable(feature = "inclusive_range", since = "1.26.0")]
impl<Idx: fmt::Debug> fmt::Debug for RangeInclusive<Idx> {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        write!(fmt, "{:?}..={:?}", self.start, self.end)
    }
}

impl<Idx: PartialOrd<Idx>> RangeInclusive<Idx> {
    /// Returns `true` if `item` is contained in the range.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(range_contains)]
    ///
    /// use std::f32;
    ///
    /// 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));
    ///
    /// assert!( (0.0..=1.0).contains(&1.0));
    /// assert!(!(0.0..=1.0).contains(&f32::NAN));
    /// assert!(!(0.0..=f32::NAN).contains(&0.0));
    /// assert!(!(f32::NAN..=1.0).contains(&1.0));
    /// ```
    #[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
    pub fn contains<U>(&self, item: &U) -> bool
    where
        Idx: PartialOrd<U>,
        U: ?Sized + PartialOrd<Idx>,
    {
        <Self as RangeBounds<Idx>>::contains(self, item)
    }

    /// Returns `true` if the range contains no items.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(range_is_empty)]
    ///
    /// assert!(!(3..=5).is_empty());
    /// assert!(!(3..=3).is_empty());
    /// assert!( (3..=2).is_empty());
    /// ```
    ///
    /// The range is empty if either side is incomparable:
    ///
    /// ```
    /// #![feature(range_is_empty)]
    ///
    /// use std::f32::NAN;
    /// assert!(!(3.0..=5.0).is_empty());
    /// assert!( (3.0..=NAN).is_empty());
    /// assert!( (NAN..=5.0).is_empty());
    /// ```
    ///
    /// This method returns `true` after iteration has finished:
    ///
    /// ```
    /// #![feature(range_is_empty)]
    ///
    /// let mut r = 3..=5;
    /// for _ in r.by_ref() {}
    /// // Precise field values are unspecified here
    /// assert!(r.is_empty());
    /// ```
    #[unstable(feature = "range_is_empty", reason = "recently added", issue = "48111")]
    pub fn is_empty(&self) -> bool {
        !(self.start <= self.end)
    }
}

/// A range only bounded inclusively above (`..=end`).
///
/// The `RangeToInclusive` `..=end` contains all values with `x <= end`.
/// It cannot serve as an [`Iterator`] because it doesn't have a starting point.
///
/// # Examples
///
/// The `..=end` syntax is a `RangeToInclusive`:
///
/// ```
/// 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
/// // error[E0277]: the trait bound `std::ops::RangeToInclusive<{integer}>:
/// // std::iter::Iterator` is not satisfied
/// 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`.
///
/// ```
/// let arr = [0, 1, 2, 3];
/// assert_eq!(arr[ ..=2], [0,1,2  ]);  // RangeToInclusive
/// assert_eq!(arr[1..=2], [  1,2  ]);
/// ```
///
/// [`IntoIterator`]: ../iter/trait.Iterator.html
/// [`Iterator`]: ../iter/trait.IntoIterator.html
/// [slicing index]: ../slice/trait.SliceIndex.html
#[doc(alias = "..=")]
#[derive(Copy, Clone, PartialEq, Eq, Hash)]
#[stable(feature = "inclusive_range", since = "1.26.0")]
pub struct RangeToInclusive<Idx> {
    /// The upper bound of the range (inclusive)
    #[stable(feature = "inclusive_range", since = "1.26.0")]
    pub end: Idx,
}

#[stable(feature = "inclusive_range", since = "1.26.0")]
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> {
    /// Returns `true` if `item` is contained in the range.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(range_contains)]
    ///
    /// use std::f32;
    ///
    /// assert!( (..=5).contains(&-1_000_000_000));
    /// assert!( (..=5).contains(&5));
    /// assert!(!(..=5).contains(&6));
    ///
    /// assert!( (..=1.0).contains(&1.0));
    /// assert!(!(..=1.0).contains(&f32::NAN));
    /// assert!(!(..=f32::NAN).contains(&0.5));
    /// ```
    #[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
    pub fn contains<U>(&self, item: &U) -> bool
    where
        Idx: PartialOrd<U>,
        U: ?Sized + PartialOrd<Idx>,
    {
        <Self as RangeBounds<Idx>>::contains(self, item)
    }
}

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

/// An endpoint of a range of keys.
///
/// # Examples
///
/// `Bound`s are range endpoints:
///
/// ```
/// #![feature(collections_range)]
///
/// use std::ops::Bound::*;
/// use std::ops::RangeBounds;
///
/// assert_eq!((..100).start(), Unbounded);
/// assert_eq!((1..12).start(), Included(&1));
/// assert_eq!((1..12).end(), Excluded(&12));
/// ```
///
/// Using a tuple of `Bound`s as an argument to [`BTreeMap::range`].
/// Note that in most cases, it's better to use range syntax (`1..5`) instead.
///
/// ```
/// use std::collections::BTreeMap;
/// use std::ops::Bound::{Excluded, Included, Unbounded};
///
/// let mut map = BTreeMap::new();
/// map.insert(3, "a");
/// map.insert(5, "b");
/// map.insert(8, "c");
///
/// for (key, value) in map.range((Excluded(3), Included(8))) {
///     println!("{}: {}", key, value);
/// }
///
/// assert_eq!(Some((&3, &"a")), map.range((Unbounded, Included(5))).next());
/// ```
///
/// [`BTreeMap::range`]: ../../std/collections/btree_map/struct.BTreeMap.html#method.range
#[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(#[stable(feature = "collections_bound", since = "1.17.0")] T),
    /// An exclusive bound.
    #[stable(feature = "collections_bound", since = "1.17.0")]
    Excluded(#[stable(feature = "collections_bound", since = "1.17.0")] T),
    /// An infinite endpoint. Indicates that there is no bound in this direction.
    #[stable(feature = "collections_bound", since = "1.17.0")]
    Unbounded,
}

#[unstable(feature = "collections_range",
           reason = "might be replaced with `Into<_>` and a type containing two `Bound` values",
           issue = "30877")]
/// `RangeBounds` is implemented by Rust's built-in range types, produced
/// by range syntax like `..`, `a..`, `..b` or `c..d`.
pub trait RangeBounds<T: ?Sized> {
    /// Start index bound.
    ///
    /// Returns the start value as a `Bound`.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(collections_range)]
    ///
    /// # fn main() {
    /// use std::ops::Bound::*;
    /// use std::ops::RangeBounds;
    ///
    /// assert_eq!((..10).start(), Unbounded);
    /// assert_eq!((3..10).start(), Included(&3));
    /// # }
    /// ```
    fn start(&self) -> Bound<&T>;

    /// End index bound.
    ///
    /// Returns the end value as a `Bound`.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(collections_range)]
    ///
    /// # fn main() {
    /// use std::ops::Bound::*;
    /// use std::ops::RangeBounds;
    ///
    /// assert_eq!((3..).end(), Unbounded);
    /// assert_eq!((3..10).end(), Excluded(&10));
    /// # }
    /// ```
    fn end(&self) -> Bound<&T>;


    /// Returns `true` if `item` is contained in the range.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(range_contains)]
    ///
    /// use std::f32;
    ///
    /// 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));
    #[unstable(feature = "range_contains", reason = "recently added as per RFC", issue = "32311")]
    fn contains<U>(&self, item: &U) -> bool
    where
        T: PartialOrd<U>,
        U: ?Sized + PartialOrd<T>,
    {
        (match self.start() {
            Included(ref start) => *start <= item,
            Excluded(ref start) => *start < item,
            Unbounded => true,
        })
        &&
        (match self.end() {
            Included(ref end) => item <= *end,
            Excluded(ref end) => item < *end,
            Unbounded => true,
        })
    }
}

use self::Bound::{Excluded, Included, Unbounded};

#[unstable(feature = "collections_range",
           reason = "might be replaced with `Into<_>` and a type containing two `Bound` values",
           issue = "30877")]
impl<T: ?Sized> RangeBounds<T> for RangeFull {
    fn start(&self) -> Bound<&T> {
        Unbounded
    }
    fn end(&self) -> Bound<&T> {
        Unbounded
    }
}

#[unstable(feature = "collections_range",
           reason = "might be replaced with `Into<_>` and a type containing two `Bound` values",
           issue = "30877")]
impl<T> RangeBounds<T> for RangeFrom<T> {
    fn start(&self) -> Bound<&T> {
        Included(&self.start)
    }
    fn end(&self) -> Bound<&T> {
        Unbounded
    }
}

#[unstable(feature = "collections_range",
           reason = "might be replaced with `Into<_>` and a type containing two `Bound` values",
           issue = "30877")]
impl<T> RangeBounds<T> for RangeTo<T> {
    fn start(&self) -> Bound<&T> {
        Unbounded
    }
    fn end(&self) -> Bound<&T> {
        Excluded(&self.end)
    }
}

#[unstable(feature = "collections_range",
           reason = "might be replaced with `Into<_>` and a type containing two `Bound` values",
           issue = "30877")]
impl<T> RangeBounds<T> for Range<T> {
    fn start(&self) -> Bound<&T> {
        Included(&self.start)
    }
    fn end(&self) -> Bound<&T> {
        Excluded(&self.end)
    }
}

#[unstable(feature = "collections_range",
           reason = "might be replaced with `Into<_>` and a type containing two `Bound` values",
           issue = "30877")]
impl<T> RangeBounds<T> for RangeInclusive<T> {
    fn start(&self) -> Bound<&T> {
        Included(&self.start)
    }
    fn end(&self) -> Bound<&T> {
        Included(&self.end)
    }
}

#[unstable(feature = "collections_range",
           reason = "might be replaced with `Into<_>` and a type containing two `Bound` values",
           issue = "30877")]
impl<T> RangeBounds<T> for RangeToInclusive<T> {
    fn start(&self) -> Bound<&T> {
        Unbounded
    }
    fn end(&self) -> Bound<&T> {
        Included(&self.end)
    }
}

#[unstable(feature = "collections_range",
           reason = "might be replaced with `Into<_>` and a type containing two `Bound` values",
           issue = "30877")]
impl<T> RangeBounds<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,
        }
    }
}

#[unstable(feature = "collections_range",
           reason = "might be replaced with `Into<_>` and a type containing two `Bound` values",
           issue = "30877")]
impl<'a, T: ?Sized + 'a> RangeBounds<T> for (Bound<&'a T>, Bound<&'a T>) {
    fn start(&self) -> Bound<&T> {
        self.0
    }

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

#[unstable(feature = "collections_range",
           reason = "might be replaced with `Into<_>` and a type containing two `Bound` values",
           issue = "30877")]
impl<'a, T> RangeBounds<T> for RangeFrom<&'a T> {
    fn start(&self) -> Bound<&T> {
        Included(self.start)
    }
    fn end(&self) -> Bound<&T> {
        Unbounded
    }
}

#[unstable(feature = "collections_range",
           reason = "might be replaced with `Into<_>` and a type containing two `Bound` values",
           issue = "30877")]
impl<'a, T> RangeBounds<T> for RangeTo<&'a T> {
    fn start(&self) -> Bound<&T> {
        Unbounded
    }
    fn end(&self) -> Bound<&T> {
        Excluded(self.end)
    }
}

#[unstable(feature = "collections_range",
           reason = "might be replaced with `Into<_>` and a type containing two `Bound` values",
           issue = "30877")]
impl<'a, T> RangeBounds<T> for Range<&'a T> {
    fn start(&self) -> Bound<&T> {
        Included(self.start)
    }
    fn end(&self) -> Bound<&T> {
        Excluded(self.end)
    }
}

#[unstable(feature = "collections_range",
           reason = "might be replaced with `Into<_>` and a type containing two `Bound` values",
           issue = "30877")]
impl<'a, T> RangeBounds<T> for RangeInclusive<&'a T> {
    fn start(&self) -> Bound<&T> {
        Included(self.start)
    }
    fn end(&self) -> Bound<&T> {
        Included(self.end)
    }
}

#[unstable(feature = "collections_range",
           reason = "might be replaced with `Into<_>` and a type containing two `Bound` values",
           issue = "30877")]
impl<'a, T> RangeBounds<T> for RangeToInclusive<&'a T> {
    fn start(&self) -> Bound<&T> {
        Unbounded
    }
    fn end(&self) -> Bound<&T> {
        Included(self.end)
    }
}