swordfishyou/mswift

Simple eDSL for Swift Optional and Array

mSwift

A simple eDSL introducing functional approach to pure calculations with Optional and Array types.

• Functions
• Currying and partial application
• Usage
  • Applicative Plain functions, Function composition, Optional
  • Binding Optional

Installation

StickyView is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod 'mSwift', :git => 'https://github.com/swordfishyou/mSwift.git'

Motivation

Functional languages like Haskell or Erlang have robust and clear syntax for pure computations. Such code is easy to understand, it's clear and doesn't break control flow. On a daily basis we don't perform pure computations, but when we do we write a lot of code. This small eDSL is designed to stay DRY in such cases.

Optional

Swift's optional binding and common usage often preferable for clarity and style. But Optional is a container type for a reason: it preserves specific context. The context is:

• it's OK for Optional value to absent,
• one doesn't use Optional for error handling.

guard let and if let force you to unwrap the box and handle the absence of a value. Moreover, so called optional binding is implemented as conditional statement, so it breaks control flow.

Array

We often use Array as a collection of objects, to keep some order, etc. Only on a rare occasion we use pure Array as designed: for non-deterministic computations.

Consider number 5. It's a deterministic value, it has just one result and we know it's 5. If we multiply it by another deterministic value like 3 we have another deterministic value 15. All these numbers have only one result. On the onther hand array [3, 5] contains two elements and if we perform multiplication by another array [1, 10, 100] we have an array with even more elements [3, 5, 30, 50, 300, 500]. Now you can see that Array is also a container type like Optional. Like any container type it also preserves a context:

• there might be multiple elements in a single Array value,
• the number of elements in a resulting Array may differ from initial values.

Since functional API is really handy we often prefer it over loops. Unfortunately, Swift lacks a number of robust sugar available in functional languages.

Implementation

mSwift introduces currying and a set of operators influenced by Haskell in order to apply functions in a pipeline.