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8e886a3bdd
The RangeProtocol was a very weak and fragile abstraction because it didn't specify the interpretation of the endpoints. To write a non-trivial algorithm, one usually needed to consult that information. The standard library code only actually worked correctly with half-open and closed ranges (and didn't handle fully open ranges, for example). The other two protocols, HalfOpenRangeProtocol and ClosedRangeProtocol, were only used for code sharing, and present an ABI burden. We can use gyb instead.
101 lines
3.0 KiB
Swift
101 lines
3.0 KiB
Swift
//===----------------------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See http://swift.org/LICENSE.txt for license information
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// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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extension String.Index {
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/// Construct the position in `characters` that corresponds exactly to
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/// `unicodeScalarIndex`. If no such position exists, the result is `nil`.
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///
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/// - Precondition: `unicodeScalarIndex` is an element of
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/// `characters.unicodeScalars.indices`.
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public init?(
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_ unicodeScalarIndex: String.UnicodeScalarIndex,
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within characters: String
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) {
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if !unicodeScalarIndex._isOnGraphemeClusterBoundary {
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return nil
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}
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self.init(_base: unicodeScalarIndex)
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}
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/// Construct the position in `characters` that corresponds exactly to
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/// `utf16Index`. If no such position exists, the result is `nil`.
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///
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/// - Precondition: `utf16Index` is an element of
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/// `characters.utf16.indices`.
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public init?(
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_ utf16Index: String.UTF16Index,
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within characters: String
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) {
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if let me = utf16Index.samePosition(
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in: characters.unicodeScalars
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)?.samePosition(in: characters) {
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self = me
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}
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else {
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return nil
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}
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}
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/// Construct the position in `characters` that corresponds exactly to
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/// `utf8Index`. If no such position exists, the result is `nil`.
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///
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/// - Precondition: `utf8Index` is an element of
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/// `characters.utf8.indices`.
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public init?(
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_ utf8Index: String.UTF8Index,
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within characters: String
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) {
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if let me = utf8Index.samePosition(
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in: characters.unicodeScalars
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)?.samePosition(in: characters) {
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self = me
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}
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else {
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return nil
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}
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}
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/// Returns the position in `utf8` that corresponds exactly
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/// to `self`.
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///
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/// - Precondition: `self` is an element of `String(utf8).indices`.
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@warn_unused_result
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public func samePosition(
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in utf8: String.UTF8View
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) -> String.UTF8View.Index {
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return String.UTF8View.Index(self, within: utf8)
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}
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/// Returns the position in `utf16` that corresponds exactly
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/// to `self`.
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///
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/// - Precondition: `self` is an element of `String(utf16).indices`.
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@warn_unused_result
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public func samePosition(
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in utf16: String.UTF16View
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) -> String.UTF16View.Index {
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return String.UTF16View.Index(self, within: utf16)
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}
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/// Returns the position in `unicodeScalars` that corresponds exactly
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/// to `self`.
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///
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/// - Precondition: `self` is an element of `String(unicodeScalars).indices`.
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@warn_unused_result
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public func samePosition(
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in unicodeScalars: String.UnicodeScalarView
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) -> String.UnicodeScalarView.Index {
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return String.UnicodeScalarView.Index(self, within: unicodeScalars)
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}
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}
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