Update Random implementation

.changeset/wet-carpets-sell.md

@@ -0,0 +1,5 @@
+---
+"@tsplus/stdlib": patch
+---
+
+update Random implementation

packages/stdlib/_src/global.ts

@@ -149,6 +149,18 @@ import { Exception } from "@tsplus/stdlib/exceptions/Exception"
  * @tsplus global
  */
 import { Eval } from "@tsplus/stdlib/io/Eval/definition"
+/**
+ * @tsplus global
+ */
+import { ArrayInt } from "@tsplus/stdlib/io/Random/Distribution/_internal/ArrayInt"
+/**
+ * @tsplus global
+ */
+import { MutableRandom } from "@tsplus/stdlib/io/Random/MutableRandom"
+/**
+ * @tsplus global
+ */
+import { PCGRandom } from "@tsplus/stdlib/io/Random/PCGRandom"
 /**
  * @tsplus global
  */
@@ -435,10 +447,6 @@ import {
  * @tsplus global
  */
 import { lazy } from "@tsplus/stdlib/utilities/Lazy"
-/**
- * @tsplus global
- */
-import { RandomPCG } from "@tsplus/stdlib/utilities/RandomPCG"
 /**
  * @tsplus global
  */

packages/stdlib/_src/io.ts

@@ -1 +1,2 @@
 export * as eval from "@tsplus/stdlib/io/Eval"
+export * as random from "@tsplus/stdlib/io/Random"

packages/stdlib/_src/io/Random.ts

@@ -0,0 +1,6 @@
+// codegen:start {preset: barrel, include: ./Random/*.ts, prefix: "@tsplus/stdlib/io"}
+export * from "@tsplus/stdlib/io/Random/Distribution"
+export * from "@tsplus/stdlib/io/Random/Generator"
+export * from "@tsplus/stdlib/io/Random/MutableRandom"
+export * from "@tsplus/stdlib/io/Random/PCGRandom"
+// codegen:end

packages/stdlib/_src/io/Random/Distribution.ts

@@ -0,0 +1,4 @@
+// codegen:start {preset: barrel, include: ./Distribution/*.ts, prefix: "@tsplus/stdlib/io/Random"}
+export * from "@tsplus/stdlib/io/Random/Distribution/definition"
+export * from "@tsplus/stdlib/io/Random/Distribution/operations"
+// codegen:end

packages/stdlib/_src/io/Random/Distribution/_internal/ArrayInt.ts

@@ -0,0 +1,201 @@
+/**
+ * An ArrayInt represents an integer larger than what can be represented in
+ * classical JavaScript.
+ *
+ * The values stored in data must be in the range `[0, 0xffffffff]`.
+ *
+ * ```ts
+ * { sign:  1, data: [ 42 ] } // = 42
+ * { sign: -1, data: [ 42 ] } // = -42
+ * { sign: -1, data: [ 5, 42 ] } // = -1 * (5 * 2**32 + 42)
+ * { sign: -1, data: [ 1, 5, 42 ] } // = -1 * (1 * 2**64 + 5 * 2**32 + 42)
+ * ```
+ */
+export interface ArrayInt {
+  /**
+   * Sign of the represented number
+   */
+  sign: -1 | 1
+  /**
+   * Value of the number, must only contain numbers in the range [0, 0xffffffff]
+   */
+  data: number[]
+}
+
+/**
+ * Add two ArrayInt
+ * @internal
+ */
+export function addArrayIntToNew(arrayIntA: ArrayInt, arrayIntB: ArrayInt): ArrayInt {
+  if (arrayIntA.sign !== arrayIntB.sign) {
+    return substractArrayIntToNew(arrayIntA, {
+      sign: -arrayIntB.sign as -1 | 1,
+      data: arrayIntB.data
+    })
+  }
+  const data = []
+  let reminder = 0
+  const dataA = arrayIntA.data
+  const dataB = arrayIntB.data
+  for (let indexA = dataA.length - 1, indexB = dataB.length - 1; indexA >= 0 || indexB >= 0; --indexA, --indexB) {
+    const vA = indexA >= 0 ? dataA[indexA]! : 0
+    const vB = indexB >= 0 ? dataB[indexB]! : 0
+    const current = vA + vB + reminder
+    data.push(current >>> 0)
+    reminder = ~~(current / 0x100000000)
+  }
+  if (reminder !== 0) {
+    data.push(reminder)
+  }
+  return { sign: arrayIntA.sign, data: data.reverse() }
+}
+
+/**
+ * Add one to a given positive ArrayInt
+ * @internal
+ */
+export function addOneToPositiveArrayInt(arrayInt: ArrayInt): ArrayInt {
+  arrayInt.sign = 1 // handling case { sign: -1, data: [0,...,0] }
+  const data = arrayInt.data
+  for (let index = data.length - 1; index >= 0; --index) {
+    if (data[index] === 0xffffffff) {
+      data[index] = 0
+    } else {
+      data[index] += 1
+      return arrayInt
+    }
+  }
+  data.unshift(1)
+  return arrayInt
+}
+
+/** @internal */
+function isStrictlySmaller(dataA: number[], dataB: number[]): boolean {
+  const maxLength = Math.max(dataA.length, dataB.length)
+  for (let index = 0; index < maxLength; ++index) {
+    const indexA = index + dataA.length - maxLength
+    const indexB = index + dataB.length - maxLength
+    const vA = indexA >= 0 ? dataA[indexA]! : 0
+    const vB = indexB >= 0 ? dataB[indexB]! : 0
+    if (vA < vB) return true
+    if (vA > vB) return false
+  }
+  return false
+}
+
+/**
+ * Substract two ArrayInt
+ * @internal
+ */
+export function substractArrayIntToNew(arrayIntA: ArrayInt, arrayIntB: ArrayInt): ArrayInt {
+  if (arrayIntA.sign !== arrayIntB.sign) {
+    return addArrayIntToNew(arrayIntA, { sign: -arrayIntB.sign as -1 | 1, data: arrayIntB.data })
+  }
+  const dataA = arrayIntA.data
+  const dataB = arrayIntB.data
+  if (isStrictlySmaller(dataA, dataB)) {
+    const out = substractArrayIntToNew(arrayIntB, arrayIntA)
+    out.sign = -out.sign as -1 | 1
+    return out
+  }
+  const data = []
+  let reminder = 0
+  for (let indexA = dataA.length - 1, indexB = dataB.length - 1; indexA >= 0 || indexB >= 0; --indexA, --indexB) {
+    const vA = indexA >= 0 ? dataA[indexA]! : 0
+    const vB = indexB >= 0 ? dataB[indexB]! : 0
+    const current = vA - vB - reminder
+    data.push(current >>> 0)
+    reminder = current < 0 ? 1 : 0
+  }
+  return { sign: arrayIntA.sign, data: data.reverse() }
+}
+
+/**
+ * Trim uneeded zeros in ArrayInt
+ * and uniform notation for zero: {sign: 1, data: [0]}
+ */
+export function trimArrayIntInplace(arrayInt: ArrayInt) {
+  const data = arrayInt.data
+  let firstNonZero = 0
+  // eslint-disable-next-line no-empty
+  for (; firstNonZero !== data.length && data[firstNonZero] === 0; ++firstNonZero) {}
+  if (firstNonZero === data.length) {
+    // only zeros
+    arrayInt.sign = 1
+    arrayInt.data = [0]
+    return arrayInt
+  }
+  data.splice(0, firstNonZero)
+  return arrayInt
+}
+
+// Helpers specific to 64 bits versions
+
+/** @internal */
+export type ArrayInt64 = Required<ArrayInt> & { data: [number, number] }
+
+/**
+ * We only accept safe integers here
+ * @internal
+ */
+export function fromNumberToArrayInt64(out: ArrayInt64, n: number): ArrayInt64 {
+  if (n < 0) {
+    const posN = -n
+    out.sign = -1
+    out.data[0] = ~~(posN / 0x100000000)
+    out.data[1] = posN >>> 0
+  } else {
+    out.sign = 1
+    out.data[0] = ~~(n / 0x100000000)
+    out.data[1] = n >>> 0
+  }
+  return out
+}
+
+/**
+ * Substract two ArrayInt of 64 bits on 64 bits.
+ * With arrayIntA - arrayIntB >= 0
+ * @internal
+ */
+export function substractArrayInt64(out: ArrayInt64, arrayIntA: ArrayInt64, arrayIntB: ArrayInt64): ArrayInt64 {
+  const lowA = arrayIntA.data[1]
+  const highA = arrayIntA.data[0]
+  const signA = arrayIntA.sign
+  const lowB = arrayIntB.data[1]
+  const highB = arrayIntB.data[0]
+  const signB = arrayIntB.sign
+
+  // Requirement: arrayIntA - arrayIntB >= 0
+  out.sign = 1
+
+  if (signA === 1 && signB === -1) {
+    // Operation is a simple sum of arrayIntA + abs(arrayIntB)
+    const low = lowA + lowB
+    const high = highA + highB + (low > 0xffffffff ? 1 : 0)
+    out.data[0] = high >>> 0
+    out.data[1] = low >>> 0
+    return out
+  }
+  // signA === -1 with signB === 1 is impossible given: arrayIntA - arrayIntB >= 0
+
+  // Operation is a substraction
+  let lowFirst = lowA
+  let highFirst = highA
+  let lowSecond = lowB
+  let highSecond = highB
+  if (signA === -1) {
+    lowFirst = lowB
+    highFirst = highB
+    lowSecond = lowA
+    highSecond = highA
+  }
+  let reminderLow = 0
+  let low = lowFirst - lowSecond
+  if (low < 0) {
+    reminderLow = 1
+    low = low >>> 0
+  }
+  out.data[0] = highFirst - highSecond - reminderLow
+  out.data[1] = low
+  return out
+}

packages/stdlib/_src/io/Random/Distribution/_internal/uniformArrayIntDistributionInternal.ts

@@ -0,0 +1,43 @@
+import type { ArrayInt } from "@tsplus/stdlib/io/Random/Distribution/_internal/ArrayInt"
+import { uniformIntDistributionInternal } from "@tsplus/stdlib/io/Random/Distribution/_internal/uniformIntDistributionInternal"
+import type { RandomGenerator } from "@tsplus/stdlib/io/Random/Generator/RandomGenerator"
+
+/**
+ * Uniformly generate an `ArrayInt` in the range [0, rangeSize].
+ *
+ * @remarks
+ * In the worst case scenario it may discard half of the randomly generated
+ * values. Worst case being: most significant number is `1` and remaining part
+ * evaluates to `0`.
+ *
+ * @internal
+ */
+export function uniformArrayIntDistributionInternal(
+  out: ArrayInt["data"],
+  rangeSize: ArrayInt["data"],
+  rng: RandomGenerator
+): ArrayInt["data"] {
+  const rangeLength = rangeSize.length
+
+  // We iterate until we find a valid value for arrayInt
+  // eslint-disable-next-line no-constant-condition
+  while (true) {
+    // We compute a new value for arrayInt
+    for (let index = 0; index !== rangeLength; ++index) {
+      const indexRangeSize = index === 0 ? rangeSize[0]! + 1 : 0x100000000
+      out[index] = uniformIntDistributionInternal(indexRangeSize, rng)
+    }
+
+    // If in the correct range we can return it
+    for (let index = 0; index !== rangeLength; ++index) {
+      const current = out[index]!
+      const currentInRange = rangeSize[index]!
+      if (current < currentInRange) {
+        return out // arrayInt < rangeSize
+      } else if (current > currentInRange) {
+        break // arrayInt > rangeSize
+      }
+    }
+    // Otherwise we need to try another one
+  }
+}

packages/stdlib/_src/io/Random/Distribution/_internal/uniformIntDistributionInternal.ts

@@ -0,0 +1,48 @@
+import type { RandomGenerator } from "@tsplus/stdlib/io/Random/Generator/RandomGenerator"
+
+/**
+ * Uniformly generate an integer in the range [0, rangeSize].
+ *
+ * @internal
+ */
+export function uniformIntDistributionInternal(rangeSize: number, rng: RandomGenerator): number {
+  const MinRng = rng.min()
+  const NumValues = rng.max() - rng.min() + 1
+
+  // Range provided by the RandomGenerator is large enough
+  if (rangeSize <= NumValues) {
+    const MaxAllowed = NumValues - (NumValues % rangeSize)
+    // eslint-disable-next-line no-constant-condition
+    while (true) {
+      const out = rng.next()
+      const deltaV = out - MinRng
+      if (deltaV < MaxAllowed) {
+        return deltaV % rangeSize // Warning: we expect NumValues <= 2**32, so diff too
+      }
+    }
+  }
+
+  // Compute number of iterations required to have enough random
+  // to build uniform entries in the asked range
+  let FinalNumValues = NumValues * NumValues
+  let NumIterations = 2 // At least 2 (at this point in the code)
+  while (FinalNumValues < rangeSize) {
+    FinalNumValues *= NumValues
+    ;++NumIterations
+  }
+  const MaxAcceptedRandom = rangeSize * Math.floor((1 * FinalNumValues) / rangeSize)
+
+  // eslint-disable-next-line no-constant-condition
+  while (true) {
+    // Aggregate mutiple calls to next() into a single random value
+    let value = 0
+    for (let num = 0; num !== NumIterations; ++num) {
+      const out = rng.next()
+      value = NumValues * value + (out - MinRng) // Warning: we overflow may when diff > max_safe (eg: =max_safe-min_safe+1)
+    }
+    if (value < MaxAcceptedRandom) {
+      const inDiff = value - rangeSize * Math.floor((1 * value) / rangeSize)
+      return inDiff
+    }
+  }
+}

packages/stdlib/_src/io/Random/Distribution/definition.ts

@@ -0,0 +1,15 @@
+import type { RandomGenerator } from "@tsplus/stdlib/io/Random/Generator/RandomGenerator"
+
+/**
+ * Generate random value based on a given RandomGenerator. Return the generated
+ * value and an offsetted version of the RandomGenerator.
+ *
+ * @tsplus type Random.Distribution
+ */
+export type Distribution<T> = (rng: RandomGenerator) => T
+
+/**
+ * @tsplus type Random.Distribution.Ops
+ */
+export interface DistributionOps {}
+export const Distribution: DistributionOps = {}

packages/stdlib/_src/io/Random/Distribution/operations.ts

@@ -0,0 +1,5 @@
+// codegen:start {preset: barrel, include: ./operations/*.ts, prefix: "@tsplus/stdlib/io/Random/Distribution"}
+export * from "@tsplus/stdlib/io/Random/Distribution/operations/uniformArrayIntDistribution"
+export * from "@tsplus/stdlib/io/Random/Distribution/operations/uniformBigIntDistribution"
+export * from "@tsplus/stdlib/io/Random/Distribution/operations/uniformIntDistribution"
+// codegen:end