Represents a pseudo-random number generator, a device that produces a sequence of numbers that meet certain statistical requirements for randomness. More...

#include <random.h>

Collaboration diagram for xtd::random:

Public Member Functions
	random ()
	Initializes a new instance of the random class, using a default generated seed value. More...

	random (uint32_t seed)
	Initializes a new instance of the random class, using a specified seed value. More...

	random (std::random_device &random_device)
	Initializes a new instance of the random class, using a specified random device value. More...

virtual int32_t	next () const
	Returns a nonnegative random number. More...

template<typename value_t >
value_t	next () const
	Returns a nonnegative random number. More...

virtual int32_t	next (int32_t max_value) const
	Returns a nonnegative random number less than the specified maximum. More...

template<typename value_t >
value_t	next (value_t max_value) const
	Returns a nonnegative random number less than the specified maximum. More...

virtual int32_t	next (int32_t min_value, int32_t max_value) const
	Returns a random number within a specified range. More...

template<typename value_t >
value_t	next (value_t min_value, value_t max_value) const
	Returns a random number within a specified range. More...

virtual void	next_bytes (std::vector< uint8_t > &buffer) const
	Fills the elements of a specified array of bytes with random numbers. More...

virtual void	next_bytes (uint8_t *buffer, size_t buffer_size) const
	Fills the elements of a specified array of bytes with random numbers. More...

virtual double	next_double () const
	Returns a random number between 0.0 and 1.0. More...

template<typename value_t >
void	next_values (std::vector< value_t > &buffer) const
	Fills the elements of a specified array of bytes with random numbers. More...

template<typename value_t >
void	next_values (value_t *buffer, size_t buffer_size) const
	Fills the elements of a specified array of bytes with random numbers. More...

Protected Member Functions
virtual double	sample () const
	Returns a random number between 0.0 and 1.0. More...

Detailed Description

Represents a pseudo-random number generator, a device that produces a sequence of numbers that meet certain statistical requirements for randomness.

Library: xtd.core

Remarks: Pseudo-random numbers are chosen with equal probability from a finite set of numbers. The chosen numbers are not completely random because a definite mathematical algorithm is used to select them, but they are sufficiently random for practical purposes. The current implementation of the random class is based on Donald E. Knuth's subtractive random number generator algorithm. For more information, see D. E. Knuth. "The Art of Computer Programming, volume 2: Seminumerical Algorithms". Addison-Wesley, Reading, MA, second edition, 1981.; The random number generation starts from a seed value. If the same seed is used repeatedly, the same series of numbers is generated. One way to produce different sequences is to make the seed value time-dependent, thereby producing a different series with each new instance of random. By default, the parameterless constructor of the random class uses the system clock to generate its seed value, while its parameterized constructor can take an int32_t value based on the number of ticks in the current time. However, because the clock has finite resolution, using the parameterless constructor to create different random objects in close succession creates random number generators that produce identical sequences of random numbers. The following example illustrates that two random objects that are instantiated in close succession generate an identical series of random numbers.
#include <xtd/xtd>
using namespace std;
using namespace xtd;
int main() {
vector<uint8_t> bytes1(100);
vector<uint8_t> bytes2(100);
xtd::random rnd1;
xtd::random rnd2;

rnd1.next_bytes(bytes1);
rnd2.next_bytes(bytes2);

console::write_line("First Series:");
for (size_t i = 0; i < bytes1.size(); i++) {
console::write("{, 5}", bytes1[i]);
if ((i + 1) % 10 == 0)
console::write_line();
}

console::write_line();
console::write_line("Second Series:");
for (size_t i = 0; i < bytes2.size(); i++) {
console::write("{, 5}", bytes2[i]);
if ((i + 1) % 10 == 0)
console::write_line();
}
}
// This code can produces the following output:
//
// First Series:
// 104 222 250 126 113 23 137 65 199 68
// 72 242 71 179 29 70 1 160 135 214
// 129 158 46 16 137 48 66 28 81 190
// 157 155 212 222 3 211 14 137 1 30
// 50 217 229 181 252 55 241 74 230 148
// 153 59 16 152 54 226 11 64 133 236
// 90 255 30 52 45 116 203 193 27 167
// 187 190 68 218 37 16 229 116 150 161
// 183 130 219 90 192 254 24 232 174 116
// 46 191 226 53 118 198 148 29 76 106
//
// Second Series:
// 104 222 250 126 113 23 137 65 199 68
// 72 242 71 179 29 70 1 160 135 214
// 129 158 46 16 137 48 66 28 81 190
// 157 155 212 222 3 211 14 137 1 30
// 50 217 229 181 252 55 241 74 230 148
// 153 59 16 152 54 226 11 64 133 236
// 90 255 30 52 45 116 203 193 27 167
// 187 190 68 218 37 16 229 116 150 161
// 183 130 219 90 192 254 24 232 174 116
// 46 191 226 53 118 198 148 29 76 106; This problem can be avoided by creating a single random object rather than multiple ones.; To improve performance, create one random object to generate many random numbers over time, instead of repeatedly creating a new random objects to generate one random number.

Notes to Callers: The implementation of the random number generator in the random class is not guaranteed to remain the same across major versions of the xtd. As a result, your application code should not assume that the same seed will result in the same pseudo-random sequence in different versions of the xtd.

Notes to Inheritors: In xtd, the behavior of the random::next(), random::next(int32_t, int32_t), and next_bytes methods have changed so that these methods do not necessarily call the derived class implementation of the sample method. As a result, classes derived from Rrandom that target the xtd should also virtual these three methods.

Examples: The following example creates a single random number generator and calls its next_bytes, next, and next_double methods to generate sequences of random numbers within different ranges.
#include <xtd/xtd>
using namespace std;
using namespace xtd;
int main() {
// Instantiate random number generator using system-supplied value as seed.
xtd::random rand;

// Generate and display 5 random uint8_t (integer) values.
vector<uint8_t> bytes(5);
rand.next_bytes(bytes);

console::write_line("Five random uint8_t values:");
for (uint8_t byte_value : bytes)
console::write("{, 5}", byte_value);
console::write_line();

// Generate and display 5 random integers.
console::write_line("Five random integer values:");
for (int ctr = 0; ctr <= 4; ctr++)
console::write("{, 15}", rand.next());
console::write_line();

// Generate and display 5 random integers between 0 and 100.//
console::write_line("Five random integers between 0 and 100:");
for (int ctr = 0; ctr <= 4; ctr++)
console::write("{, 10}", rand.next(101));
console::write_line();

// Generate and display 5 random integers from 50 to 100.
console::write_line("Five random integers between 50 and 100:");
for (int ctr = 0; ctr <= 4; ctr++)
console::write("{, 10}", rand.next(50, 101));
console::write_line();

// Generate and display 5 random floating point values from 0 to 1.
console::write_line("Five Doubles:");
for (int ctr = 0; ctr <= 4; ctr++)
console::write("{, 10}", rand.next_double());
console::write_line();

// Generate and display 5 random floating point values from 0 to 5.
console::write_line("Five Doubles between 0 and 5:");
for (int ctr = 0; ctr <= 4; ctr++)
console::write("{, 10}", rand.next_double() * 5);
console::write_line();
}
// This code can produces the following output:
//
// Five random uint8_t values:
// 150 243 92 141 0
// Five random integer values:
// 4.14343E+08 2.14086E+09 1.73486E+09 1.88133E+09 1.69685E+09
// Five random integers between 0 and 100:
// 35 86 86 68 10
// Five random integers between 50 and 100:
// 76 57 66 97 56
// Five Doubles:
// 0.211096 0.172007 0.507414 0.48576 0.754658
// Five Doubles between 0 and 5:
// 1.40691 2.7078 3.87732 1.0691 0.478343

Examples: The following example generates a random integer that it uses as an index to retrieve a string value from an array.
#include <xtd/xtd>
using namespace std;
using namespace xtd;
int main() {
xtd::random rnd;
vector<string> male_pet_names = {"Rufus", "Bear", "Dakota", "Fido", "Vanya", "Samuel", "Koani", "Volodya", "Prince", "Yiska"};
vector<string> female_pet_names = {"Maggie", "Penny", "Saya", "Princess", "Abby", "Laila", "Sadie", "Olivia", "Starlight", "Talla"};

// Generate random indexes for pet names.
size_t male_index = rnd.next(male_pet_names.size());
size_t female_index = rnd.next(female_pet_names.size());

// Display the result.
console::write_line("Suggested pet name of the day: ");
console::write_line(" For a male: {0}", male_pet_names[male_index]);
console::write_line(" For a female: {0}", female_pet_names[female_index]);
}
// This code can produces the following output:
//
// Suggested pet name of the day:
// For a male: Prince
// For a female: Talla

The documentation for this class was generated from the following file:

random.h

Public Member Functions

Protected Member Functions

Detailed Description