myReduce.swift

extension Sequence {
    /// Reduce: applies a given operation on elements of a given sequence and returns a single value (of same type as of the elements in given sequence) at the end
    /// - Parameters:
    ///   - initialValue: Initial value for the operation to start
    ///   - operation: function that'll be applied on elements of the given sequence
    /// - Returns: final value after applying operation on the elements of given sequence
    func myReduce(_ initialValue: Element,
                  _ operation: (_ value1: Element, _ value2: Element) -> Element) -> Element {
        
        var output: Element = initialValue
        
        for item in self {
            output = operation(output, item)
        }
        
        return output        
    }
}