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swift-prelude

Swift 5.1 CI @pointfreeco

A collection of frameworks to enhance the Swift language.

Stability

This library should be considered experimental. If you find its contents useful, please consider maintaining a fork.

Installation

import PackageDescription

let package = Package(
  dependencies: [
    .package(url: "https://github.com/pointfreeco/swift-prelude.git", .branch("main")),
  ]
)

Table of Contents

Prelude

A collection of types and functions to build powerful abstractions and enhance the Swift standard library.

Either

A type to express a value that holds one of two other types.

import Either

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

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

Optics

A Lens type and a bridge between the lens world and the Swift key path world.

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")

ValidationSemigroup

The Validation<E, A> type is a type similar to Result<E, A>, except it is given a different applicative instance in the case that E is a semigroup. This allows you to accumulate multiple errors into E instead of just taking the first error:

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."])

For more information, watch Stephen Celisā€™ talk.

ValidationNearSemiring

This Validation<E, A> type is a type similar to Result<E, A> and the above Validation, except it is given a different applicative instance in the case that E is a NearSemiring. This allows you to accumulate errors that describe conditions that hold with both ā€œandā€ and ā€œorā€, e.g. name is required and either email or phone is required.

License

All modules are released under the MIT license. See LICENSE for details.

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šŸŽ¶ A collection of types and functions that enhance the Swift language.

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