swift-prelude

import PackageDescription

let package = Package(
  dependencies: [
    .package(
      url: "https://github.com/capturecontext/swift-prelude.git",
      .upToNextMinor(from: "0.2.0")
    ),
  ]
)

import Either

let intOrString = Either<Int, String>.left(2)

intOrString
  .bimap({ $0 + 1 }, { $0 + "!" }) // => .left(3)

import Optics
import Prelude

struct User {
  var id: Int
  var name: String
}

let uppercased: (String) -> String = { $0.uppercased() }

let user = User(id: 1, name: "Blob")

user
  |> \.id .~ 2
  |> \.name %~ uppercased

// => User(2, "BLOB")

import Prelude
import ValidationSemigroup

struct User { let name: String; let bio: String; let email: String }
let createUser = { name in { bio in { email in User(name: name, bio: bio, email: email) } } }

func validate(name: String) -> Validation<[String], String> {
  return !name.isEmpty
    ? pure(name)
    : .invalid(["Name must be at least 1 character."])
}

func validate(bio: String) -> Validation<[String], String> {
  return bio.count <= 10
    ? pure(bio)
    : .invalid(["Bio must 10 characters or less."])
}

func validate(email: String) -> Validation<[String], String> {
  return email.contains("@")
    ? pure(email)
    : .invalid(["Email must be valid."])
}

let validUser = pure(createUser)
  <*> validate(name: "Blob")
  <*> validate(bio: "I'm a blob")
  <*> validate(email: "blob@pointfree.co")
// => .valid(User(name: "Blob", bio: "I'm a blob", email: "blob@pointfree.co"))

let invalidUser = pure(createUser)
  <*> validate(name: "Blob")
  <*> validate(bio: "Blobbin around the world")
  <*> validate(email: "blob")
// => .invalid(["Bio must 10 characters or less.", "Email must be valid."])