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Create RandomRetrievable protocols
Types that conform to RandomRetrievable can have any random element be taken from an instance. The `uncheckedRandom(using:)` method is unsafe. It is a serious programming error to use it on an empty sequence. The RandomRetrievableInRange protocol allows for getting random elements from within a given index range. It is also a serious programming error to use `uncheckedRandom(in:using:)` when the sequence or range is empty or the range is out of bounds. This removes `random(using:)` that could previously be used on any Sequence. In theory, any Sequence can conform to RandomRetrievable and RandomRetrievableInRange given Array's conformance to these protocols. However, it would hide the horrible performance involved with allocating memory for all elements of a sequence just to get a single random value out. This is even worse when multiple random values are needed and thus multiple arrays are allocated. Types such as lazy sequence types will be able to conform to these protocols once conditional conformance is implemented (SE-0143).
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‎RandomKit.xcodeproj/project.pbxproj

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14+
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15+
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16+
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17+
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@@ -149,10 +153,6 @@
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@@ -297,6 +297,7 @@
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524083961CA5B31E00AB8851 /* RandomKit.playground */ = {isa = PBXFileReference; lastKnownFileType = file.playground; path = RandomKit.playground; sourceTree = "<group>"; };
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@@ -314,7 +315,6 @@
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@@ -471,6 +471,7 @@
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@@ -501,7 +502,6 @@
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@@ -953,6 +953,7 @@
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524F1E0F1E312E2A00BDE35F /* RandomToValue.swift in Sources */,
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524F1E541E31360500BDE35F /* Character+RandomKit.swift in Sources */,
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5247B99F1E890BB200C6B60E /* RandomRetrievable.swift in Sources */,
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52CA18211E63A818004C18FA /* NSArray+RandomKit.swift in Sources */,
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52D47D431E315D860050588E /* Strideable+RandomKit.swift in Sources */,
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524F1E071E312E0600BDE35F /* RandomWithMax.swift in Sources */,
@@ -1079,7 +1080,6 @@
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524F1E3B1E31312900BDE35F /* Integer+RandomKit.swift in Sources */,
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524F1E231E312F8200BDE35F /* RandomWithExactWidth.swift in Sources */,
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524F1E1F1E312F6100BDE35F /* RandomWithMaxWidth.swift in Sources */,
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52485F691E3FEE11007C53AC /* StackArray.swift in Sources */,
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524F1E271E312FCF00BDE35F /* UniqueShuffleable.swift in Sources */,
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5290FC581E7C5AFA008CA2AA /* ReseedingRandomGenerator.swift in Sources */,
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524F1E591E31364D00BDE35F /* Array+RandomKit.swift in Sources */,
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524F1E101E312E2A00BDE35F /* RandomToValue.swift in Sources */,
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524F1E551E31360600BDE35F /* Character+RandomKit.swift in Sources */,
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5247B9A01E890BB200C6B60E /* RandomRetrievable.swift in Sources */,
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52CA18221E63A818004C18FA /* NSArray+RandomKit.swift in Sources */,
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52D47D441E315D870050588E /* Strideable+RandomKit.swift in Sources */,
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524F1E081E312E0600BDE35F /* RandomWithMax.swift in Sources */,
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524F1E3C1E31312A00BDE35F /* Integer+RandomKit.swift in Sources */,
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524F1E241E312F8200BDE35F /* RandomWithExactWidth.swift in Sources */,
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524F1E201E312F6100BDE35F /* RandomWithMaxWidth.swift in Sources */,
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52485F6A1E3FEE11007C53AC /* StackArray.swift in Sources */,
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524F1E281E312FD000BDE35F /* UniqueShuffleable.swift in Sources */,
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5290FC591E7C5AFA008CA2AA /* ReseedingRandomGenerator.swift in Sources */,

‎Sources/RandomKit/Extensions/Foundation/NSArray+RandomKit.swift

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import Foundation
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extension NSArray {
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/// Returns a random element of `self`, or `nil` if `self` is empty.
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public func random<R: RandomGenerator>(using randomGenerator: inout R) -> Any? {
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let count = self.count
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guard count > 0 else {
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extension NSArray: RandomRetrievableInRange {
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/// Returns a random element in `range` without checking whether `self` or `range` is empty.
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public func uncheckedRandom<R: RandomGenerator>(in range: Range<Int>, using randomGenerator: inout R) -> Any {
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let index = Int.uncheckedRandom(within: range, using: &randomGenerator)
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return self[index]
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}
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/// Returns a random element in `self` without checking whether `self` is empty.
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public func uncheckedRandom<R: RandomGenerator>(using randomGenerator: inout R) -> Any {
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return uncheckedRandom(in: Range(uncheckedBounds: (0, count)), using: &randomGenerator)
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}
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/// Returns an optional random element in `range`. The result is `nil` if `self` or `range` is empty.
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public func random<R: RandomGenerator>(in range: Range<Int>, using randomGenerator: inout R) -> Any? {
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guard count > 0 && range.upperBound > range.lowerBound else {
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return nil
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}
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return self[Int.random(to: count, using: &randomGenerator)]
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return uncheckedRandom(in: range, using: &randomGenerator)
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}
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/// Returns an optional random element in `self`. The result is `nil` if `self` is empty.
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public func random<R: RandomGenerator>(using randomGenerator: inout R) -> Any? {
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return count > 0 ? uncheckedRandom(using: &randomGenerator) : nil
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}
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}
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extension NSMutableArray: ShuffleableInRange, UniqueShuffleableInRange {

‎Sources/RandomKit/Extensions/Swift/Array+RandomKit.swift

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@@ -142,32 +142,6 @@ extension Array where Element: RandomWithinClosedRange {
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}
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}
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#if !swift(>=3.1)
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extension ContiguousArray {
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/// Returns a random element of `self`, or `nil` if `self` is empty.
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public func random<R: RandomGenerator>(using randomGenerator: inout R) -> Element? {
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guard let index = _indexRange.random(using: &randomGenerator) else {
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return nil
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}
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return _buffer.firstElementAddress[index]
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}
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}
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extension Array {
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/// Returns a random element of `self`, or `nil` if `self` is empty.
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public func random<R: RandomGenerator>(using randomGenerator: inout R) -> Element? {
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guard let index = _indexRange.random(using: &randomGenerator) else {
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return nil
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}
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if let address = _buffer.firstElementAddressIfContiguous {
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return address[index]
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} else {
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return self[index]
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}
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}
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}
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#endif
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extension Array {
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/// Returns an array of randomly choosen elements.

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