This Week’s Program: Oct 17 - Oct 21

I spent a bit of time this week reading the rules of Necromunda and expanding hive-city a bit more. No animated gif though; a lot of what I worked on was under the hood. Check out the code I wrote this week!

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I flesh out the Turn module a bit more. A turn in both Necromunda and Warhammer 40K is broken up into a series of phases. A player can only do certain actions depending on the phase.

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Here, I make it so that you can only move a Model if you’re in the Movement phase of the Turn. I also do a little trick I saw in Richard Feldman’s elm-conf talk, Making Impossible States Impossible. In this talk, Richard walks through using Elm’s Sum Types (aka Algebraic Data Types) to hide implementation details. I use that in the Turn type:

type Turn = Turn Int Phase

This basically says that a Turn type has 1 constructor, also called Turn, that takes an Int and a Phase. Within the Turn module, I can deconstruct on this, but I don’t expose the Turn constructor outside of the module. Only functions within the Turn module can create new turns.

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There are four different types of fighters in Necromunda: Gangers, Heavies, Juves, and Leaders. Each one of these types start off with a base level attributes. I formalize those a bit more.

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I apply the same constructor type pattern from the Turn type to the Gang type. Previously, a Gang was just a Dict — a key/value pair. Now, a Gang has a rich set of information, but that information is only accessible from using functions from the Gang module. Nothing changes in the API, all the functions keep their type signatures, but the implementation details are all different. Now a Gang can also “recruit” members. In Necromunda, you’re given a certain number of “Guilder credits” that you can use to “buy” gang members and weapons. In this way, you can bring the same Gang from game to game and power them up over time. I make it so that recruiting new Models deducts points from your available credits in the recruit function.

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Here’s a new module: Action. An Action is a thing a Model is doing: either awaiting instructions, moving, shooting, etc.

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The Player type is always performing some Action. When the Player selects a Model, then the Action is rendered. Typically, the Player is performing the Await action, which just means that the selected Model is awaiting some instruction.

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When the Player clicks on the screen, if they’re not 2 inches near the selected Model, the Model will be deselected. I make the Tabletop.isWithinDistance function to handle that scenario.

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When you hit the “1” through “5” keys on your keyboard, that selects the corresponding Gang member. I expose Gang.toArray to make this easier. You’ll notice I’m really loving Elm’s pipeline operator (|>) and using Maybe.map and Maybe.withDefault together. That pattern is used all throughout this program.

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There’s a lot going on here. When a Player has the Await action, selecting a Model will render a small little control that shows the available actions that Model can take in the current Phase. This code sets that up and also sets up the control for Move. When the Move control is clicked, the Player is now in the Move action and renders the measuring tape UI. Now when the Player clicks and the current action is Move, it moves the Model just as it had done before.

Harry’s, my employer, is having a Chili cookoff today. So I’m going to go enjoy that now. Have a good weekend!

🌶 Mark