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최후의 종교전쟁: 클로저와 하스켈의 대결


서문
세상은 두 진영으로 나누어졌다. 하나는 순수 함수의 정수를 믿으며, 모든 부작용을 멀리하는 하스켈의 추종자들이었다. 
다른 하나는 Lisp의 유연한 철학과 매크로의 강력함을 무기로 삼는 클로저의 신도들이었다. 
이야기는 먼 미래, 신성 코드의 영역에서 두 진영의 최후의 종교전쟁이 시작됨으로써 펼쳐진다.

장: 1 - 불꽃 튀는 시작
코드의 성역에서 펼쳐진 회의는 긴장으로 가득 찼다. 하스켈 대사제인 휴이드는 자신의 깨끗하고 우아한 타입 시스템을 높이 치켜들었다.

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This tutorial explains how Unison handles 'effectful' computations, like storing state or performing I/O, using abilities. It assumes you haven't come across abilities before, and covers everything from the ground up.

This is an unofficial tutorial, written before the one on unisonweb.org/docs. The approach taken here is slow and methodical. Your first stop should be the official tutorial, if you haven't seen it already.

This doc is a Unison transcript - the source is here.

Terminology note: other languages with ability systems typically call them 'effect handlers' or 'algebraic effects', but many of the ideas are the same.

Introducing abilities

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package zero

import izumi.reflect.Tag
import Kyo.*
import scala.collection.View.FlatMap

type Id[T]    = T
type Const[T] = [U] =>> T
type MX[T]    = Any

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// Adapted from http://lukajcb.github.io/blog/functional/2018/01/03/optimizing-tagless-final.html

import { Applicative, Applicative1 } from 'fp-ts/lib/Applicative'
import { Apply, Apply1, Apply2C, applySecond, liftA4 } from 'fp-ts/lib/Apply'
import * as array from 'fp-ts/lib/Array'
import * as const_ from 'fp-ts/lib/Const'
import { HKT, Type, Type2, URIS, URIS2 } from 'fp-ts/lib/HKT'
import { IO, io, URI as IOURI } from 'fp-ts/lib/IO'
import { Option, some } from 'fp-ts/lib/Option'
import { getProductSemigroup, Semigroup } from 'fp-ts/lib/Semigroup'

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import { log } from 'fp-ts/lib/Console'
import { none, Option, some } from 'fp-ts/lib/Option'
import { randomInt } from 'fp-ts/lib/Random'
import { fromIO, Task, task } from 'fp-ts/lib/Task'
import { createInterface } from 'readline'

//
// helpers
//

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import { log } from 'fp-ts/lib/Console'
import { Type, URIS } from 'fp-ts/lib/HKT'
import { none, Option, some } from 'fp-ts/lib/Option'
import { randomInt } from 'fp-ts/lib/Random'
import { fromIO, Task, task, URI as TaskURI } from 'fp-ts/lib/Task'
import { createInterface } from 'readline'

//
// helpers
//

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{
  "compilerOptions": {
    
    // Base Strict Checks
    "suppressExcessPropertyErrors": false,
    "suppressImplicitAnyIndexErrors": false,
    "noStrictGenericChecks": false    
    
    // Strict Checks
    "alwaysStrict": true, 

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// originally written by evolu
// https://twitter.com/evoluhq/status/1530920057303449601/photo/1

import { flow } from 'fp-ts/lib/function'
import * as E from 'fp-ts/lib/Either'
import * as SRTE from 'fp-ts/lib/StateReaderTaskEither'
import {StateReaderTaskEither} from 'fp-ts/lib/StateReaderTaskEither'

type Config = {logs : string[]}
type Deps = {multiplier : number}