Bow is a library for Typed Functional Programming in Swift.


Bow is split in multiple modules that can be consumed independently. These modules are:

  • Bow: core library. Contains Higher Kinded Types emulation, function manipulation utilities, Typeclasses, Data Types, Monad Transformers and instances for primitive types.
  • BowOptics: module to work with different optics.
  • BowRecursionSchemes: module to work with recursion schemes.
  • BowFree: module to work with Free Monads.
  • BowGeneric: module to work with generic data types.
  • BowEffects: module to work with effects.
  • BowBrightFutures: module to provide an integration with BrightFutures.
  • BowRx: module to provide an integration with RxSwift.

There are also some modules for testing:

  • BowLaws: laws for type classes in the core module.
  • BowOpticsLaws: laws for optics.
  • BowEffectsLaws: laws for effects.
  • BowGenerators: generators for Property-based Testing for data types in the core module.
  • BowFreeGenerators: generators for Property-based Testing for data types in BowFree.
  • BowEffectsGenerators: generators for Property-based Testing for data types in BowEffects.
  • BowRxGenerators: generators for Property-based Testing for data types in BowRx.
  • BowBrightFuturesGenerators: generators for Property-based Testing for data types in BowBrightFutures.

Bow is available using CocoaPods, Carthage and Swift Package Manager.


You can consume each Bow module as a separate pod. You can add these lines to your Podfile at your convenience:

pod "Bow",                 "~> {version}"
pod "BowOptics",           "~> {version}"
pod "BowRecursionSchemes", "~> {version}"
pod "BowFree",             "~> {version}"
pod "BowGeneric",          "~> {version}"
pod "BowEffects",          "~> {version}"
pod "BowRx",               "~> {version}"
pod "BowBrightFutures",    "~> {version}"

Testing laws:

pod "BowLaws",        "~> {version}"
pod "BowOpticsLaws",  "~> {version}"
pod "BowEffectsLaws", "~> {version}"

Generators for property-based testing with SwiftCheck:

pod "BowGenerators",              "~> {version}"
pod "BowFreeGenerators",          "~> {version}"
pod "BowEffectsGenerators",       "~> {version}"
pod "BowRxGenerators",            "~> {version}"
pod "BowBrightFuturesGenerators", "~> {version}"


Carthage will download the whole Bow project, but it will compile individual frameworks for each module that you can use separately. Add this line to your Cartfile:

github "bow-swift/Bow" ~> {version}

Swift Package Manager

Create a Package.swift file similar to the next one and use the dependencies at your convenience.

// swift-tools-version:5.0

import PackageDescription

let package = Package(
    name: "BowTestProject",
    dependencies: [
        .package(url: "", from: "{version}")
    targets: [
        .target(name: "BowTestProject",
                dependencies: [
        .testTarget(name: "BowTestProjectTests",
                    dependencies: [
                        // Type class laws

                        // Generators for PBT with SwiftCheck

To build it, just run:

$ swift build


If you want to contribute to this library, you can check the Issues to see some of the pending task.

How to run the project

If you don’t have carthage, install it first:

brew install carthage

After this, grab all the project dependencies running:

carthage bootstrap

Now, you can open Bow.xcodeproj with Xcode and run the test to see that everything is working.


Copyright (C) 2018 The Bow Authors

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
See the License for the specific language governing permissions and
limitations under the License.