Adds an arbitrary amount of ledgers together.

const wallet = Map({GOLD: 0});
const expensesLedger = Map({GOLD: -5});
const profitsLedger = Map({GOLD: 10, Silver: 3 });

const total = sum(wallet, expensesLedger, profitsLedger);
total.get("GOLD");   // 5
total.get("SILVER"); // 3

const ledgers = [wallet, expenses, profits];
const total = sum(...ledgers);

Multiplies all currency values in a ledger by the scale. This is quite useful for when you want to multiply the effects of an item by the amount of that item.

const incomeFromSalesfolk = Map({GOLD: 2, INFLUENCE: 5});
const newIncome = scale(incomeFromSalesFolk, state.numOfSalesfolk);

newIncome.get("GOLD");     // 2 * state.numOfSalesfolk
newIncome.get("INFLUENCE") // 5 * state.numOfSalesfolk

Returns true if all items in the ledger are positive.

Returns true if all items in the ledger are negative.

Returns all unique currencies defined in several ledgers

Gets the currency value of a particular currency given several ledgers. This is useful for finding the cost of something spread over several different ledgers.

const materialCost = Map({GOLD: -5, SILVER: -2});
const transportCost = Map({GOLD: -2});
const goldCost = totalOf("GOLD", materialCost, transportCost); // -7

Given an item, run it's cost function and return the result.

Given a bunch of items, figure out all their costs and return it as an immutable Map

Buy returns a new wallet after an item is purchased. If the item is free, it just returns the same wallet.

const MagicSword = {
  type: "MagicSword",
  cost: state => Map({ GOLD: -(5 + state.marketPrice) })
}

const wallet = new Map({ GOLD: 10 });
const state = { marketPrice : 1 };

const newWallet = buy(MagicSword, wallet, state); // Gold => 4
const canBuy = inTheBlack(newWallet); // true

Adds an item to the wallet

const MagicSword = {
  type: "MagicSword"
}
const wallet = new Map({GOLD: 10})

add(MagicSword, wallet);    // Map({GOLD: 10, MagicSword: 1})
add(MagicSword, wallet, 3); // Map({GOLD: 10, MagicSword: 3})

For a collection of items, combines their "effect" functions into one big ledger. This is useful for caching the onUpdate effects to your wallet rather than computing them every time.

const pouch = {
  MagicSword: {
    type: "MagicSword",
    effect: state => doSomething(state)
  },
  // ...
}

const ledger = effects(pouch, wallet, state);