Functional Programming With Physics

This playground received a Swift Student Challenge 2021 Award. It introduces functional pipline concepts (map and filter) using a Rube Goldberg-inspired physics simulation. It also provides an easy API for you to create your own pipeline simulations.

Demo

We can simulate this pipeline:

[8, 7, 9, 10, 4, 6, 5]
    .filter { $0.isMultiple(of: 2) }
    .map { $0 / 2 }

By executing the following code in the playground:

PlaygroundPage.current.setLiveView(
    Simulation(
        source: [8, 7, 9, 10, 4, 6, 5],
        pipeline: [
            Filter(expression: "input is even"),
            Map(expression: "input ÷ 2")
        ]
    )
)

Which generates the following user-controlled simulation:

API Notes

Simulation can be initialised with any integer sequence, so the following is valid:

Simulation(source: 1...10, pipeline: /*...*/)

Some example expressions you can use:

PlaygroundPage.current.setLiveView(
    Simulation(
        source: /*...*/,
        pipeline: [
            Filter(expression: "input is odd"),
            Filter(expression: "input is prime"),
            Filter(expression: "input is negative"),
            Filter(expression: "input ≠ 5"),
            Filter(expression: "input is square")
        ]
    )
)

Acknowledgements

Expression by Nick Lockwood helps keep the simulation API easy to use.