WoExecutable.swift

import UIKit

protocol WoExecutable {
    func を<Result>(_ process: WoProcess<Self, Result>) -> Result
}

extension WoExecutable {
    func を<Result>(_ process: WoProcess<Self, Result>) -> Result {
        return process.process(self)
    }
}

struct WoProcess<Element, Result> {
    var process: (_ e: Element) -> Result
}

extension Array: WoExecutable { }

let つなげる = WoProcess<[String], String>(process: { $0.joined() })
let 足し合わせる = WoProcess<[Int], Int>(process: { $0.reduce(0, +) })
let 数える = WoProcess<[Int], Int>(process: { $0.count })

["hoge", "hoge"].を(つなげる)
[1, 2, 3, 4, 5].を(足し合わせる)
[1, 2, 3, 4, 5].を(数える)