     
     /// Map only every nth element of a sequence, leaving other elements untransformed
     func mapEveryNth(n: Int, _ transform: (S.Generator.Element) -> S.Generator.Element) -> LazySequence<MapSequenceView<EnumerateSequence<LazyBidirectionalCollection<S>>,S.Generator.Element>> {
-        return self.mapIfIndex(transform, isMultipleOf(n) • { $0 + 1 })
+        return self.mapIfIndex(transform, isMultipleOf(n) • inc )
     }
 }
 

    return source.mapEveryNth(n, transform)
}


    
    /// Map only every nth element of a sequence, leaving other elements untransformed
    func mapEveryNth(n: Int, _ transform: (S.Generator.Element) -> S.Generator.Element) -> LazySequence<MapSequenceView<EnumerateSequence<LazyForwardCollection<S>>,S.Generator.Element>> {
        return self.mapIfIndex(transform, isMultipleOf(n) • inc)
    }
}

