feat(boolean): add random boolean generator with optional bias

packages/boolean/src/RandomBoolean/index.ts

@@ -0,0 +1,41 @@
+import { RandomEngine } from '@grandom/core'
+
+export default class RandomBoolean {
+  private _engine: RandomEngine
+
+  constructor (engine: RandomEngine) {
+    this._engine = engine
+  }
+
+  /**
+   * A1
+   */
+  boolean (): boolean
+
+  /**
+   * B1
+   */
+  boolean (bias: number): boolean
+
+  boolean (arg1?: any): boolean {
+    if (typeof arg1 !== 'undefined') {
+      if (typeof arg1 !== 'number') {
+        throw new TypeError(`bias must be a number, got: ${typeof arg1}.`)
+      }
+
+      // NaN guard
+      if (arg1 === arg1) {
+        if (arg1 < 0) {
+          arg1 = 0
+        } else if (arg1 > 1) {
+          arg1 = 1
+        }
+
+        // return this._engine.nextDouble() < arg1
+        return this._engine.nextFloat() < arg1
+      }
+    }
+
+    return this._engine.nextBoolean()
+  }
+}

packages/boolean/src/index.ts

@@ -1,4 +1,7 @@
-export const boolean = (): number => {
+import { BasicEngine } from '@grandom/engines'
+import RandomBoolean from './RandomBoolean'
 
-  throw new Error('Unimplemented.')
-}
+const random = new RandomBoolean(new BasicEngine())
+const boolean = random.boolean.bind(random)
+
+export default boolean