add more math and random shortcuts

Author: dmonad

array.js

@@ -20,3 +20,16 @@ export const create = () => []
  * @return {Array<T>}
  */
 export const copy = a => a.slice()
+
+/**
+ * Append elements from src to dest
+ *
+ * @template T
+ * @param {Array<T>} dest
+ * @param {Array<T>} src
+ */
+export const appendTo = (dest, src) => {
+  for (let i = 0; i < src.length; i++) {
+    dest.push(src[i])
+  }
+}

math.js

@@ -4,8 +4,11 @@
 export const floor = Math.floor
 export const ceil = Math.ceil
 export const abs = Math.abs
-
+export const imul = Math.imul
 export const round = Math.round
+export const log10 = Math.log10
+export const log2 = Math.log2
+export const log = Math.log
 
 /**
  * @function

prng.test.js

@@ -8,6 +8,7 @@ import { Xorshift32 } from './prng/Xorshift32.js'
 import { Mt19937 } from './prng/Mt19937.js'
 import * as dom from './dom.js'
 import { isBrowser, production } from './environment.js'
+import * as math from './math.js'
 
 const genTestData = 5000
 
@@ -31,8 +32,8 @@ const runGenTest = (tc, gen) => {
       }
     }
     t.info(`Generated ${head} heads and ${tail} tails.`)
-    t.assert(tail >= Math.floor(genTestData * 0.45), 'Generated enough tails.')
-    t.assert(head >= Math.floor(genTestData * 0.45), 'Generated enough heads.')
+    t.assert(tail >= math.floor(genTestData * 0.45), 'Generated enough tails.')
+    t.assert(head >= math.floor(genTestData * 0.45), 'Generated enough heads.')
   })
   t.group('int31 - integers average correctly', () => {
     let count = 0
@@ -44,7 +45,7 @@ const runGenTest = (tc, gen) => {
     const average = count / genTestData
     const expectedAverage = 100 / 2
     t.info(`Average is: ${average}. Expected average is ${expectedAverage}.`)
-    t.assert(Math.abs(average - expectedAverage) <= 2, 'Expected average is at most 1 off.')
+    t.assert(math.abs(average - expectedAverage) <= 2, 'Expected average is at most 1 off.')
   })
 
   t.group('int32 - generates integer with 32 bits', () => {

prng/Mt19937.js

@@ -1,4 +1,5 @@
 import * as binary from '../binary.js'
+import * as math from '../math.js'
 
 /**
  * @module prng
@@ -48,7 +49,7 @@ export class Mt19937 {
     const state = new Uint32Array(N)
     state[0] = seed
     for (let i = 1; i < N; i++) {
-      state[i] = (Math.imul(1812433253, (state[i - 1] ^ (state[i - 1] >>> 30))) + i) & binary.BITS32
+      state[i] = (math.imul(1812433253, (state[i - 1] ^ (state[i - 1] >>> 30))) + i) & binary.BITS32
     }
     this._state = state
     this._i = 0

random.js

@@ -5,6 +5,12 @@
  */
 import * as env from './environment.js'
 import * as binary from './binary.js'
+import * as math from './math.js'
+
+/**
+ * Basically Math.random. Returns a pseudo random number in [0,1).
+ */
+const rand = Math.random
 
 /* istanbul ignore next */
 const uint32BrowserCrypto = () => {
@@ -14,7 +20,7 @@ const uint32BrowserCrypto = () => {
 }
 
 /* istanbul ignore next */
-const uint32NoCrypto = () => Math.ceil((Math.random() * binary.BITS32) >>> 0)
+const uint32NoCrypto = () => math.ceil((rand() * binary.BITS32) >>> 0)
 
 /**
  * @param {typeof import('crypto')} crypto
@@ -30,3 +36,10 @@ const uint32NodeCrypto = crypto => () => {
 export const uint32 = env.isBrowser
   ? (typeof crypto === 'undefined' ? uint32NoCrypto : uint32BrowserCrypto)
   : uint32NodeCrypto(require('crypto'))
+
+/**
+ * @template T
+ * @param {Array<T>} arr
+ * @return {T}
+ */
+export const oneOf = arr => arr[math.floor(rand() * arr.length)]