Use a function to find common elements in two sequences in Swift

swift

Solution

I was able to get it to work by making the return value an Array of T.GeneratorType.Element.

func anyCommonElements <T, U where T: SequenceType, U: SequenceType, T.Generator.Element: Equatable, T.Generator.Element == U.Generator.Element> (lhs: T, rhs: U) -> Array<T.Generator.Element> {
    var toReturn = Array<T.Generator.Element>()
    for lhsItem in lhs {
        for rhsItem in rhs {
            if lhsItem == rhsItem {
                toReturn.append(lhsItem)
            }
        }
    }
    return toReturn
}
anyCommonElements([1, 2, 3], [3])

Problem

I'm trying to complete the exercise on page 46 of Apple's new book "The Swift Programming Language". It gives the following code: ``` func anyCommonElements <T, U where T: Sequence, U: Sequence, T.GeneratorType.Element: Equatable, T.GeneratorType.Element == U.GeneratorType.Element> (lhs: T, rhs: U) -> Bool { for lhsItem in lhs { for rhsItem in rhs { if lhsItem == rhsItem { return true } } } return false } anyCommonElements([1, 2, 3], [3]) ``` The exercise is to change the function so that all elements that both sequences have are returned. To do this I tried to use the following code: ``` func anyCommonElements <T, U where T: Sequence, U: Sequence, T.GeneratorType.Element: Equatable, T.GeneratorType.Element == U.GeneratorType.Element> (lhs: T, rhs: U) -> T.GeneratorType[] { var toReturn = T.GeneratorType[]() for lhsItem in lhs { for rhsItem in rhs { if lhsItem == rhsItem { toReturn.append(lhsItem) } } } return toReturn } anyCommonElements([1, 2, 3], [3]) ``` But on line 2, I get the error: Could not find the member 'subscript' What is the reason for this error and what is the best solution to this problem?

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