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Add samples for Random.nextX() functions

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This commit is contained in:
Kris
2020-10-07 15:48:55 -05:00
committed by Abduqodiri Qurbonzoda
parent ebdd023633
commit 173954b3b3
2 changed files with 133 additions and 1 deletions
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libraries/stdlib/samples/test/samples/random/randoms.kt
+103 -1
View File
@@ -6,6 +6,7 @@
package samples.random
import samples.*
import kotlin.math.sin
import kotlin.random.Random
import kotlin.test.assertTrue
@@ -38,4 +39,105 @@ class Randoms {
// random with another seed produce another sequence
assertPrints(randomValues3, "[14, 48, 57, 67, 82, 7, 61, 27, 14, 59]")
}
}
@Sample
fun nextBits() {
// always generates a 0
println(Random.nextBits(0))
// randomly generates a 0 or 1
println(Random.nextBits(1))
// generates a random non-negative Int value less than 256
println(Random.nextBits(8))
// generates a random Int value, may generate a negative value as well
println(Random.nextBits(32))
}
@Sample
fun nextBoolean() {
val presents = listOf("Candy", "Balloon", "Ball")
// a random partition, the result may be different every time
val (alicePresents, bobPresents) = presents.partition { Random.nextBoolean() }
println("Alice receives $alicePresents")
println("Bob receives $bobPresents")
}
@Sample
fun nextBytes() {
val bytes = ByteArray(4)
assertPrints(bytes.contentToString(), "[0, 0, 0, 0]")
Random.nextBytes(bytes, 1, 3)
// second and third bytes are generated, rest unchanged
println(bytes.contentToString())
Random.nextBytes(bytes)
// all bytes are newly generated
println(bytes.contentToString())
val newBytes = Random.nextBytes(5)
// a new byte array filled with random values
println(newBytes.contentToString())
}
@Sample
fun nextDouble() {
if (Random.nextDouble() <= 0.3) {
println("There was 30% possibility of rainy weather today and it is raining.")
} else {
println("There was 70% possibility of sunny weather today and the sun is shining.")
}
}
@Sample
fun nextDoubleFromUntil() {
val firstAngle = Random.nextDouble(until = Math.PI / 6);
assertTrue(sin(firstAngle) < 0.5)
val secondAngle = Random.nextDouble(from = Math.PI / 6, until = Math.PI / 2)
val sinValue = sin(secondAngle)
assertTrue(sinValue >= 0.5 && sinValue < 1.0)
}
@Sample
fun nextFloat() {
if (Random.nextFloat() <= 0.3) {
println("There was 30% possibility of rainy weather today and it is raining.")
} else {
println("There was 70% possibility of sunny weather today and the sun is shining.")
}
}
@Sample
fun nextInt() {
val randomInts = List(5) { Random.nextInt() }
println(randomInts)
val sortedRandomInts = randomInts.sorted()
println(sortedRandomInts)
}
@Sample
fun nextIntFromUntil() {
val menu = listOf("Omelette", "Porridge", "Cereal", "Chicken", "Pizza", "Pasta")
val forBreakfast = Random.nextInt(until = 3).let { menu[it] }
val forLunch = Random.nextInt(from = 3, until = 6).let { menu[it] }
// new meals every time
println("Today I want $forBreakfast for breakfast, and $forLunch for lunch.")
}
@Sample
fun nextLong() {
val randomLongs = List(5) { Random.nextLong() }
println(randomLongs)
val sortedRandomLongs = randomLongs.sorted()
println(sortedRandomLongs)
}
@Sample
fun nextLongFromUntil() {
val fileSize = Random.nextLong(until = 1_099_511_627_776)
println("A file of $fileSize bytes fits on a 1TB storage.")
val long = Random.nextLong(Int.MAX_VALUE + 1L, Long.MAX_VALUE)
println("Number $long doesn't fit in an Int.")
}
}
libraries/stdlib/src/kotlin/random/Random.kt
+30
View File
@@ -25,6 +25,8 @@ public abstract class Random {
* Generates an `Int` whose lower [bitCount] bits are filled with random values and the remaining upper bits are zero.
*
* @param bitCount number of bits to generate, must be in range 0..32, otherwise the behavior is unspecified.
*
* @sample samples.random.Randoms.nextBits
*/
public abstract fun nextBits(bitCount: Int): Int
@@ -32,6 +34,8 @@ public abstract class Random {
* Gets the next random `Int` from the random number generator.
*
* Generates an `Int` random value uniformly distributed between `Int.MIN_VALUE` and `Int.MAX_VALUE` (inclusive).
*
* @sample samples.random.Randoms.nextInt
*/
public open fun nextInt(): Int = nextBits(32)
@@ -43,6 +47,8 @@ public abstract class Random {
* @param until must be positive.
*
* @throws IllegalArgumentException if [until] is negative or zero.
*
* @sample samples.random.Randoms.nextIntFromUntil
*/
public open fun nextInt(until: Int): Int = nextInt(0, until)
@@ -52,6 +58,8 @@ public abstract class Random {
* Generates an `Int` random value uniformly distributed between the specified [from] (inclusive) and [until] (exclusive) bounds.
*
* @throws IllegalArgumentException if [from] is greater than or equal to [until].
*
* @sample samples.random.Randoms.nextIntFromUntil
*/
public open fun nextInt(from: Int, until: Int): Int {
checkRangeBounds(from, until)
@@ -81,6 +89,8 @@ public abstract class Random {
* Gets the next random `Long` from the random number generator.
*
* Generates a `Long` random value uniformly distributed between `Long.MIN_VALUE` and `Long.MAX_VALUE` (inclusive).
*
* @sample samples.random.Randoms.nextLong
*/
public open fun nextLong(): Long = nextInt().toLong().shl(32) + nextInt()
@@ -92,6 +102,8 @@ public abstract class Random {
* @param until must be positive.
*
* @throws IllegalArgumentException if [until] is negative or zero.
*
* @sample samples.random.Randoms.nextLongFromUntil
*/
public open fun nextLong(until: Long): Long = nextLong(0, until)
@@ -101,6 +113,8 @@ public abstract class Random {
* Generates a `Long` random value uniformly distributed between the specified [from] (inclusive) and [until] (exclusive) bounds.
*
* @throws IllegalArgumentException if [from] is greater than or equal to [until].
*
* @sample samples.random.Randoms.nextLongFromUntil
*/
public open fun nextLong(from: Long, until: Long): Long {
checkRangeBounds(from, until)
@@ -143,11 +157,15 @@ public abstract class Random {
/**
* Gets the next random [Boolean] value.
*
* @sample samples.random.Randoms.nextBoolean
*/
public open fun nextBoolean(): Boolean = nextBits(1) != 0
/**
* Gets the next random [Double] value uniformly distributed between 0 (inclusive) and 1 (exclusive).
*
* @sample samples.random.Randoms.nextDouble
*/
public open fun nextDouble(): Double = doubleFromParts(nextBits(26), nextBits(27))
@@ -157,6 +175,8 @@ public abstract class Random {
* Generates a `Double` random value uniformly distributed between 0 (inclusive) and [until] (exclusive).
*
* @throws IllegalArgumentException if [until] is negative or zero.
*
* @sample samples.random.Randoms.nextDoubleFromUntil
*/
public open fun nextDouble(until: Double): Double = nextDouble(0.0, until)
@@ -168,6 +188,8 @@ public abstract class Random {
* [from] and [until] must be finite otherwise the behavior is unspecified.
*
* @throws IllegalArgumentException if [from] is greater than or equal to [until].
*
* @sample samples.random.Randoms.nextDoubleFromUntil
*/
public open fun nextDouble(from: Double, until: Double): Double {
checkRangeBounds(from, until)
@@ -183,6 +205,8 @@ public abstract class Random {
/**
* Gets the next random [Float] value uniformly distributed between 0 (inclusive) and 1 (exclusive).
*
* @sample samples.random.Randoms.nextFloat
*/
public open fun nextFloat(): Float = nextBits(24) / (1 shl 24).toFloat()
@@ -191,6 +215,8 @@ public abstract class Random {
* with random bytes.
*
* @return [array] with the subrange filled with random bytes.
*
* @sample samples.random.Randoms.nextBytes
*/
public open fun nextBytes(array: ByteArray, fromIndex: Int = 0, toIndex: Int = array.size): ByteArray {
require(fromIndex in 0..array.size && toIndex in 0..array.size) { "fromIndex ($fromIndex) or toIndex ($toIndex) are out of range: 0..${array.size}." }
@@ -221,11 +247,15 @@ public abstract class Random {
* Fills the specified byte [array] with random bytes and returns it.
*
* @return [array] filled with random bytes.
*
* @sample samples.random.Randoms.nextBytes
*/
public open fun nextBytes(array: ByteArray): ByteArray = nextBytes(array, 0, array.size)
/**
* Creates a byte array of the specified [size], filled with random bytes.
*
* @sample samples.random.Randoms.nextBytes
*/
public open fun nextBytes(size: Int): ByteArray = nextBytes(ByteArray(size))