add unbiased coin

README.md

@@ -1,4 +1,5 @@
 # Fortuna
+The quick solution for everything random!
 
 A Gacha-like system to roll random items with weights.
 

deno.json

@@ -1,6 +1,16 @@
 {
-    "tasks": {
-        "bench": "deno bench --unstable benches/comparison.ts",
-        "test": "deno test test.ts"
+    "bench": {
+        "files": {
+            "include": [
+                "./benches/comparison.ts"
+            ]
+        }
+    },
+    "test": {
+        "files": {
+            "include": [
+                "./test.ts"
+            ]
+        }
     }
 }

dist/coin.js

@@ -0,0 +1,10 @@
+// deno-fmt-ignore-file
+// deno-lint-ignore-file
+// This code was bundled using `deno bundle` and it's not recommended to edit it manually
+
+function unbiasedCoin(n = 1) {
+    const upperBound = 1 << n;
+    const res = Math.floor(Math.random() * upperBound).toString(2).padStart(n, "0");
+    return res.split("").map((x)=>x === "0" ? "H" : "T");
+}
+export { unbiasedCoin as unbiasedCoin };

mod.ts

@@ -2,3 +2,4 @@ export { GachaMachine } from "./src/machine.ts";
 export { LimitedGachaMachine } from "./src/limited_machine.ts";
 export { rollDie } from "./src/die.ts";
 export { roll } from "./src/roll.ts";
+export { unbiasedCoin } from "./src/coin.ts"

src/coin.ts

@@ -0,0 +1,12 @@
+// A biased coin can be implemented using GachaMachine.
+
+/**
+ * Toss n unbiased coins (50% chance of head / tail).
+ * @param n Number of coins to toss.
+ * @returns Array of results. Returns "H" for head and "T" for tail.
+ */
+export function unbiasedCoin(n = 1): ("H" | "T")[] {
+    const upperBound = 1 << n
+    const res = Math.floor(Math.random() * upperBound).toString(2).padStart(n, "0")
+    return res.split("").map(x => x === "0" ? "H" : "T")
+}

src/die.ts

@@ -1,3 +1,5 @@
+// A biased die can be implemented using GachaMachine.
+
 export interface DieConfig {
   times: number;
   face: number;

test.ts

@@ -6,6 +6,7 @@ import {
   assertThrows,
 } from "https://deno.land/[email protected]/testing/asserts.ts";
 import { GachaMachine, LimitedGachaMachine, roll, rollDie } from "./mod.ts";
+import { unbiasedCoin } from "./src/coin.ts";
 
 const testData = [
   { result: "SSR cool character", chance: 1 },
@@ -183,6 +184,22 @@ Deno.test({
   },
 });
 
+Deno.test({
+  name: `Toss an unbiased coin (should return ["H"] or ["T"])`,
+  fn() {
+    const res = unbiasedCoin();
+    assert(res.length === 1 && res[0] === "H" || res[0] === "T");
+  },
+});
+
+Deno.test({
+  name: `Toss N unbiased coins (should return an array of "H" or "T")`,
+  fn() {
+    const res = unbiasedCoin();
+    assert(res.length === 1 && res.every((x) => x === "H" || x === "T"));
+  },
+});
+
 /*
 Deno.test({
     name: `${sortedTestData[0].chance} in ${testData.reduce((acc, val) => acc + val.chance, 0)} rolls return a ${sortedTestData[0].result}?`,