Sequence Extension

SequenceExtention.swift

extension Sequence {
    public func inspect(_ body: (Element) throws -> Void) rethrows  -> Self {
        for element in self {
            try body(element)
        }
        return self
    }
    
}
extension Sequence {
    func scan<Result>(
        initialResult: Result,
        _ nextPartialResult: (Result, Element) throws -> Result
        ) rethrows -> [Result] {
        var iterator = makeIterator()

        var results = ContiguousArray<Result>()
        var accumulated: Result = initialResult
        while let element = iterator.next() {
            accumulated = try nextPartialResult(accumulated, element)
            results.append(accumulated)
        }

        return Array(results)
    }
}

// 1. 
["C", "B", "A", "D"]
    .sorted()
    .inspect { (string) in
        print("Inspecting: \(string)")
    }.filter { (string) -> Bool in
        string < "C"
    }.forEach {
        print("Result: \($0)")
    }
// 2.
let results = (0..<5).scan(initialResult: "") { (result: String, int:
 Int) -> String in
        return "\(result)\(int)"
}
print(results) // ["0", "01", "012", "0123", "01234"]

let lowercased = ["S", "W", "I", "F", "T"].scan(initialResult: "") { 
 (result: String, string: String) -> String in
    return "\(result)\(string.lowercased())"
}

print(lowercased) // ["s", "sw", "swi", "swif", "swift"]