Currying Implementation with swift

Currying.swift

//
//  Currying.swift
//
//  Created by Joshua on 2020/01/12.
//  Copyright © 2020 Joshua. All rights reserved.
//
import Foundation

precedencegroup Currying { // 왼쪽에서 오른쪽 방향으로 적용
    associativity: left
}

infix operator |>: Currying // Currying 연산자
infix operator |>>: Currying // 함수 실행 연산자
infix operator <|: Currying // 클로저 획득 연산자
// MARK:- Function Object
// 인자가 없는 함수
struct Function0<R> {
    let closure: () -> R

    private func trigger() -> R {
        return closure()
    }

    static func |>> (_ a: Function0<R>, _ param: ()) -> R {
        return a.trigger()
    }

    static func <|(_ function: Function0<R>, _ param: ()) -> () -> R {
        return function.closure
    }

    static func |><R2>(_ f :Function0<R>, _ closure : @escaping (R) -> R2 ) -> Function0<R2> {
        let result = {
            closure(f.trigger())
        }
        return Function0<R2>(closure: result)
    }
}

// 인자가 1개 있는 함수
struct Function1<A, R> {
    let closure: (A) -> R

    private func curry(_ a: A) -> Function0<R> {
        let result = {
            self.closure(a)
        }

        return Function0(closure: result)
    }

    fileprivate func trigger(_ a: A) -> R {
        return closure(a)
    }

    // 인자 하나를 받아 인자 하나가 적은 Function객체를 반환한다.
    static func |> (_ f :Function1<A, R>, _ a: A) -> Function0<R> {
        return f.curry(a)
    }

    // 필요한 인자를 Tuple 형태로 넘겨받아 실행한다.
    static func |>> (_ a: Function1<A,R>, _ param: (A)) -> R {
        return a.trigger(param)
    }

    // Function 객체가 가진 클로저 자체를 반환한다.
    static func <|(_ function: Function1<A, R>, _ param: ()) -> (A) -> R {
        return function.closure
    }

    // 반환값을 인자로 받는 클로저를 받아서 Function 객체의 반환값의 타입을 변화시킨다.
    static func |><R2>(_ f :Function1<A, R>, _ closure : @escaping (R) -> R2 ) -> Function1<A, R2> {
        let result = { a in
            closure(f.trigger(a))
        }
        return Function1<A, R2>(closure: result)
    }
}

struct Function2<A, B, R> {
    let closure: (A, B) -> R

    private func curry(_ a: A) -> Function1<B, R> {
        let result = { b in
            self.closure(a, b)
        }

        return Function1(closure: result)
    }

    private func trigger(_ a: A, _ b: B) -> R {
        return closure(a, b)
    }

    static func |> (_ f :Function2<A, B, R>, _ a: A) -> Function1<B, R> {
        return f.curry(a)
    }

    static func |>> (_ a: Function2<A, B, R>, _ param: (A, B)) -> R {
        return a.trigger(param.0, param.1)
    }

    static func <|(_ function: Function2<A, B, R>, _ param: ()) -> (A, B) -> R {
        return function.closure
    }

    static func |><R2>(_ f :Function2<A, B, R>, _ closure : @escaping (R) -> R2 ) -> Function2<A, B, R2> {
        let result = { a, b in
            closure(f.trigger(a, b))
        }
        return Function2<A, B, R2>(closure: result)
    }
}

struct Function3<A, B, C, R> {
    let closure: (A, B, C) -> R

    private func curry(_ a: A) -> Function2<B, C, R> {
        let result = { b, c in
            self.closure(a, b, c)
        }

        return Function2(closure: result)
    }

    private func trigger(_ a: A, _ b: B, _ c: C) -> R {
        return closure(a, b, c)
    }

    static func |> (_ f :Function3<A, B, C, R>, _ a: A) -> Function2<B, C, R> {
        return f.curry(a)
    }

    static func |>> (_ a: Function3<A, B, C, R>, _ param: (A, B, C)) -> R {
        return a.trigger(param.0, param.1, param.2)
    }

    static func <|(_ function: Function3<A, B, C, R>, _ param: ()) -> (A, B, C) -> R {
        return function.closure
    }

    static func |><R2>(_ f :Function3<A, B, C, R>, _ closure : @escaping (R) -> R2 ) -> Function3<A, B, C, R2> {
        let result = { a, b, c in
            closure(f.trigger(a, b, c))
        }
        return Function3<A, B, C, R2>(closure: result)
    }
}

struct Function4<A, B, C, D, R> {
    let closure: (A, B, C, D) -> R

    private func curry(_ a: A) -> Function3<B, C, D, R> {
        let result = { b, c, d in
            self.closure(a, b, c, d)
        }

        return Function3(closure: result)
    }

    private func trigger(_ a: A, _ b: B, _ c: C, _ d: D) -> R {
        return closure(a, b, c, d)
    }

    static func |> (_ f :Function4<A, B, C, D, R>, _ a: A) -> Function3<B, C, D, R> {
        return f.curry(a)
    }

    static func |>> (_ a: Function4<A, B, C, D, R>, _ param: (A, B, C, D)) -> R {
        return a.trigger(param.0, param.1, param.2, param.3)
    }

    static func <|(_ function: Function4<A, B, C, D, R>, _ param: ()) -> (A, B, C, D) -> R {
        return function.closure
    }

    static func |><R2>(_ f :Function4<A, B, C, D, R>, _ closure : @escaping (R) -> R2 ) -> Function4<A, B, C, D, R2> {
        let result = { a, b, c, d in
            closure(f.trigger(a, b, c, d))
        }
        return Function4<A, B, C, D, R2>(closure: result)
    }
}

struct Function5<A, B, C, D, E, R> {
    let closure: (A, B, C, D, E) -> R

    private func curry(_ a: A) -> Function4<B, C, D, E, R> {
        let result = { b, c, d, e in
            self.closure(a, b, c, d, e)
        }

        return Function4(closure: result)
    }

    private func trigger(_ a: A, _ b: B, _ c: C, _ d: D, _ e: E) -> R {
        return closure(a, b, c, d, e)
    }

    static func |> (_ f :Function5<A, B, C, D, E, R>, _ a: A) -> Function4<B, C, D, E, R> {
        return f.curry(a)
    }

    static func |>> (_ a: Function5<A, B, C, D, E, R>, _ param: (A, B, C, D, E)) -> R {
        return a.trigger(param.0, param.1, param.2, param.3, param.4)
    }

    static func <|(_ function: Function5<A, B, C, D, E, R>, _ param: ()) -> (A, B, C, D, E) -> R {
        return function.closure
    }

    static func |><R2>(_ f :Function5<A, B, C, D, E, R>, _ closure : @escaping (R) -> R2 ) -> Function5<A, B, C, D, E, R2> {
        let result = { a, b, c, d, e in
            closure(f.trigger(a, b, c, d, e))
        }
        return Function5<A, B, C, D, E, R2>(closure: result)
    }
}

// MARK:- Function Object Maker
// 클로저를 받아서 Function 객체로 만들어준다.
func function<A, B, C, D, E, R>(_ function: @escaping (A, B, C, D, E) -> R) -> Function5<A, B, C, D, E, R> {
    return Function5(closure: function)
}

func function<A, B, C, D, R>(_ function: @escaping (A, B, C, D) -> R) -> Function4<A, B, C, D, R> {
    return Function4(closure: function)
}

func function<A, B, C, R>(_ function: @escaping (A, B, C) -> R, _ a: A) -> Function3<A, B, C, R> {
    return Function3(closure: function)
}

func function<A, B, R>(_ function: @escaping (A, B) -> R) -> Function2<A, B, R> {
    return Function2(closure: function)
}

func function<A, R>(_ function: @escaping (A) -> R) -> Function1<A, R> {
    return Function1(closure: function)
}

func function<R>(_ function: @escaping ()->R) -> Function0<R> {
    return Function0(closure: function)
}

Example.swift

import Foundation

let result1: Int = function(max)
    |> 10
    |> 5
    |>> ()

print(result1) // 10

let result2: Int = function(max)
    |> 11
    |>> (5)

print(result2) // 11

let maxWith12 = function(max)
    |> 12
    <| ()

print(maxWith12(18))