And now, proper random decimals implementation

src/main/kotlin/ru/dbotthepony/mc/otm/core/RandomUtils.kt

@@ -4,9 +4,10 @@ import it.unimi.dsi.fastutil.ints.IntList
 import net.minecraft.Util
 import net.minecraft.util.RandomSource
 import ru.dbotthepony.mc.otm.core.math.Decimal
+import java.math.BigInteger
 import java.util.*
 import java.util.random.RandomGenerator
-import kotlin.NoSuchElementException
+import kotlin.experimental.and
 import kotlin.math.ln
 import kotlin.math.sqrt
 
@@ -103,14 +104,116 @@ fun <T> List<T>.random(random: RandomSource): T {
 	return get(random.nextInt(size))
 }
 
-fun RandomSource.nextDecimal(min: Decimal, max: Decimal, round: Boolean = false): Decimal {
+class RandomByteSource(private val source: RandomSource) {
-	val value = nextDouble()
+	private val bytes = ByteArray(8)
+	private var i = 7
 
-	return if (round) {
+	fun next(): Byte {
-		Decimal((min + (max - min) * value).whole)
+		if (++i == 8) {
-	} else {
+			i = 0
-		min + (max - min) * value
+
+			var generate = source.nextLong()
+
+			for (i in 0 .. 7) {
+				bytes[i] = generate.toByte()
+				generate = generate ushr 8
 			}
+		}
+
+		return bytes[i]
+	}
+
+	fun next(bound: Int): Byte {
+		require(bound > 0) { "Bound must be positive" }
+		val m = bound - 1
+		var r = next().toInt().and(0xFF)
+
+		if (bound and m == 0) {
+			r = r and m
+		} else {
+			var u = r ushr 1
+
+			while (true) {
+				r = u % bound
+
+				if (u + m - r < 0) {
+					u = next().toInt().and(0xFF).ushr(1)
+				} else {
+					break
+				}
+			}
+		}
+
+		return r.toByte()
+	}
+
+	fun next(bytes: ByteArray) {
+		for (i in bytes.indices) {
+			bytes[i] = next()
+		}
+	}
+}
+
+/**
+ * Uniformely distributed [Decimal] value on [0,[bound]) range
+ *
+ * If [round] is `true`, will only return integers
+ */
+fun RandomSource.nextDecimal(bound: Decimal, round: Boolean = false): Decimal {
+	if (round)
+		require(bound > Decimal.ZERO) { "Bound must be positive, $bound given" }
+	else
+		require(bound >= Decimal.ONE) { "Bound must be 1 or bigger, $bound given" }
+
+	require(bound.isFinite) { "Bound must be finite" }
+
+	val bytes = RandomByteSource(this)
+
+	if (round) {
+		val thisBytes = bound.whole.toByteArray()
+		val generateBytes = ByteArray(thisBytes.size)
+		bytes.next(generateBytes)
+
+		generateBytes[0] = generateBytes[0].and(127)
+
+		if (generateBytes[0] >= thisBytes[0]) {
+			generateBytes[0] = bytes.next(thisBytes[0].toInt().and(127))
+		}
+
+		return Decimal(BigInteger(generateBytes))
+	} else {
+		val thisBytes = bound.mag.toByteArray()
+		val generateBytes = ByteArray(thisBytes.size)
+		bytes.next(generateBytes)
+
+		generateBytes[0] = generateBytes[0].and(127)
+
+		if (generateBytes[0] >= thisBytes[0]) {
+			generateBytes[0] = bytes.next(thisBytes[0].toInt().and(127))
+		}
+
+		return Decimal.raw(BigInteger(generateBytes))
+	}
+}
+
+/**
+ * Uniformely distributed [Decimal] value on [[origin],[bound]) range
+ *
+ * If [round] is `true`, will only return integers
+ */
+fun RandomSource.nextDecimal(origin: Decimal, bound: Decimal, round: Boolean = false): Decimal {
+	require(origin < bound) { "Origin must be less than bound: $origin < $bound" }
+	require(origin.isFinite) { "Origin must be finite" }
+	require(bound.isFinite) { "Bound must be finite" }
+
+	return origin + nextDecimal(bound - origin, round)
+}
+
+/**
+ * Uniformely distributed [Decimal] value on [0,1) range
+ */
+fun RandomSource.nextDecimal(): Decimal {
+	return nextDecimal(Decimal.ZERO, Decimal.ONE)
 }
 
 fun RandomSource.nextVariance(value: Decimal, round: Boolean = false): Decimal {

src/main/kotlin/ru/dbotthepony/mc/otm/core/math/Decimal.kt

@@ -39,6 +39,8 @@ sealed class Decimal : Number(), Comparable<Decimal> {
 	 */
 	abstract val fractional: BigInteger
 
+	abstract internal val mag: BigInteger
+
 	/**
 	 * *Signed* normalized (-1,1) fractional part of this Decimal, as [Float]
 	 */
@@ -181,7 +183,7 @@ sealed class Decimal : Number(), Comparable<Decimal> {
 		return toBigDecmial().divide(divisor.toBigDecmial(), PERCENTAGE_CONTEXT).toFloat()
 	}
 
-	private class Regular(val mag: BigInteger, marker: Nothing?) : Decimal() {
+	private class Regular(override val mag: BigInteger, marker: Nothing?) : Decimal() {
 		constructor(value: BigInteger) : this(value * PRECISION_POW_BI, null)
 		constructor(value: BigDecimal) : this(value.setScale(PRECISION, RoundingMode.HALF_UP).unscaledValue(), null)
 		constructor(value: Float) : this(BigDecimal.valueOf(value.toDouble()))
@@ -703,6 +705,9 @@ sealed class Decimal : Number(), Comparable<Decimal> {
 	}
 
 	private object PositiveInfinity : Decimal() {
+		override val mag: BigInteger
+			get() = throw UnsupportedOperationException()
+
 		private fun readResolve(): Any = PositiveInfinity
 
 		override val isInfinite: Boolean
@@ -952,6 +957,9 @@ sealed class Decimal : Number(), Comparable<Decimal> {
 	}
 
 	private object NegativeInfinity : Decimal() {
+		override val mag: BigInteger
+			get() = throw UnsupportedOperationException()
+
 		private fun readResolve(): Any = NegativeInfinity
 
 		override val isInfinite: Boolean
@@ -1195,6 +1203,9 @@ sealed class Decimal : Number(), Comparable<Decimal> {
 	}
 
 	private object Zero : Decimal() {
+		override val mag: BigInteger
+			get() = BigInteger.ZERO
+
 		private fun readResolve(): Any = Zero
 
 		override val isInfinite: Boolean