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[stdlib] moving String.CharacterView.Index._predecessor/_successor to index(before:)/index(after:)

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This commit is contained in:
Max Moiseev
2016-05-17 14:14:30 -07:00
parent 6552ac823d
commit 9baaccdeae
1 changed files with 16 additions and 28 deletions
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44
stdlib/public/core/StringCharacterView.swift
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@@ -93,29 +93,6 @@ extension String.CharacterView : BidirectionalCollection {
self._countUTF16 = _countUTF16
}
/// Returns the next consecutive value after `self`.
///
/// - Precondition: The next value is representable.
// FIXME: swift-3-indexing-model: pull the following logic into UTF8View.index(after: Index)
internal func _successor() -> Index {
_precondition(_base != _base._viewEndIndex, "cannot increment endIndex")
return Index(_base: _endBase)
}
/// Returns the previous consecutive value before `self`.
///
/// - Precondition: The previous value is representable.
// FIXME: swift-3-indexing-model: pull the following logic into UTF8View.index(before: Index)
internal func _predecessor() -> Index {
_precondition(_base != _base._viewStartIndex,
"cannot decrement startIndex")
let predecessorLengthUTF16 =
Index._measureExtendedGraphemeClusterBackward(from: _base)
return Index(
_base: UnicodeScalarView.Index(
_utf16Index - predecessorLengthUTF16, _base._core))
}
internal let _base: UnicodeScalarView.Index
/// The count of this extended grapheme cluster in UTF-16 code units.
@@ -238,17 +215,28 @@ extension String.CharacterView : BidirectionalCollection {
return Index(_base: unicodeScalars.endIndex)
}
// TODO: swift-3-indexing-model - add docs
/// Returns the next consecutive position after `i`.
///
/// - Precondition: The next position is valid.
@warn_unused_result
public func index(after i: Index) -> Index {
// FIXME: swift-3-indexing-model: range check i?
return i._successor()
_precondition(i._base != i._base._viewEndIndex, "cannot increment endIndex")
return Index(_base: i._endBase)
}
// TODO: swift-3-indexing-model - add docs
/// Returns the previous consecutive position before `i`.
///
/// - Precondition: The previous position is valid.
@warn_unused_result
public func index(before i: Index) -> Index {
return i._predecessor()
// FIXME: swift-3-indexing-model: range check i?
_precondition(i._base != i._base._viewStartIndex,
"cannot decrement startIndex")
let predecessorLengthUTF16 =
Index._measureExtendedGraphemeClusterBackward(from: i._base)
return Index(
_base: UnicodeScalarView.Index(
i._utf16Index - predecessorLengthUTF16, i._base._core))
}
/// Access the `Character` at `position`.