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Add Range[Inclusive]::is_empty

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During the RFC, it was discussed that figuring out whether a range is empty was subtle, and thus there should be a clear and obvious way to do it.  It can't just be ExactSizeIterator::is_empty (also unstable) because not all ranges are ExactSize -- not even Range<i32> or RangeInclusive<usize>.
This commit is contained in:
Scott McMurray 2018-02-09 01:47:18 -08:00
parent afa8acce25
commit 4f8049a2b0
5 changed files with 62 additions and 5 deletions
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4
src/libcore/tests/iter.rs
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@ -1427,9 +1427,9 @@ fn test_range_inclusive_nth() {
assert_eq!(r, 13..=20);
assert_eq!(r.nth(2), Some(15));
assert_eq!(r, 16..=20);
assert_eq!(r.is_empty(), false);
assert_eq!(ExactSizeIterator::is_empty(&r), false);
assert_eq!(r.nth(10), None);
assert_eq!(r.is_empty(), true);
assert_eq!(ExactSizeIterator::is_empty(&r), true);
assert_eq!(r, 1..=0); // We may not want to document/promise this detail
}