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extension SequenceType { | |
var headTail: (Generator.Element, AnySequence<Generator.Element>)? { | |
var g = self.generate() | |
return g.next().map{($0, AnySequence{g})} | |
} | |
func scan<U>(initial: U, combine: (U, Generator.Element) -> U) -> [U] { | |
var prev = initial | |
return self.map{prev = combine(prev, $0); return prev} | |
} | |
func scan(combine: (Generator.Element, Generator.Element) -> Generator.Element) -> [Generator.Element]? { | |
return self.headTail.map{$1.scan($0, combine: combine)} | |
} | |
func reduce(combine: (Generator.Element, Generator.Element) -> Generator.Element) -> Generator.Element? { | |
return self.headTail.map{$1.reduce($0, combine: combine)} | |
} | |
func all(condition: Generator.Element -> Bool) -> Bool { | |
return !self.contains{!condition($0)} | |
} | |
} | |
protocol Lazy: SequenceType {} | |
extension LazySequence: Lazy {} | |
extension LazyBidirectionalCollection: Lazy {} | |
extension LazyForwardCollection: Lazy {} | |
extension LazyRandomAccessCollection: Lazy {} | |
extension Lazy { | |
var headTail: (Generator.Element, LazySequence<AnySequence<Generator.Element>>)? { | |
var g = self.generate() | |
return g.next().map{($0, lazy(AnySequence{g}))} | |
} | |
func scan<U>(initial: U, combine: (U, Generator.Element) -> U) -> LazySequence<AnyGenerator<U>> { | |
var (prev, g) = (initial, self.generate()) | |
return lazy( anyGenerator { g.next().map { prev = combine(prev, $0); return prev } } ) | |
} | |
func scan(combine: (Generator.Element, Generator.Element) -> Generator.Element) -> LazySequence<AnyGenerator<Generator.Element>>? { | |
return self.headTail.map{$1.scan($0, combine: combine)} | |
} | |
func reduce(combine: (Generator.Element, Generator.Element) -> Generator.Element) -> Generator.Element? { | |
return self.headTail.map{$1.reduce($0, combine: combine)} | |
} | |
} |
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