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Programming-Idioms

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Idiom #15 Pick uniformly a random integer in [a..b]

Pick a random integer greater than or equals to a, inferior or equals to b. Precondition : a < b.

real :: c
integer :: res

call random_number(c)
res = int((b-a+1)*c)

with Ada.Numerics.Discrete_Random;
declare
   subtype Random_Range is Integer range A .. B;
   package Rand is
      new Ada.Numerics.Discrete_Random (Random_Range);
   use Rand;
   Gen    : Generator;
   Result : Random_Range;
begin
   Reset (Gen);
   Result := Random (Gen);
end;
#include <stdlib.h>
int pick(int a, int b)
{
	int upper_bound = b - a + 1;
	int max = RAND_MAX - RAND_MAX % upper_bound;
	int r;

	do {
		r = rand();
	} while (r >= max);
	r = r % upper_bound;
	return a + r;
}

(+ a (rand-int (- b a)))
#include <random>
std::mt19937 gen;
std::uniform_int_distribution<size_t> uid (a, b);
uid (gen);

using System;
Random r = new Random();
return r.Next(a, b + 1);
using System;
Random.Shared.Next(a, b + 1)
import std.random;
auto x1 = uniform(a, b+1);
auto x2 = uniform!"[]"(a, b);
import 'dart:math';
int pick(int a, int b) => a + Random().nextInt(b - a + 1);
:crypto.rand_uniform(a, b)
a - 1 + :rand.uniform(b-a+1)
crypto:rand_uniform(A, B)
import "math/rand"
func pick(a,b int) int {
	return a + rand.Intn(b-a+1)
}
import "math/rand/v2"
func pick(a, b int) int {
	return a + rand.IntN(b-a+1)
}
import System.Random
let pick (a, b) = randomRIO (a, b) :: IO Integer
 in pick (1, 6) >>= print


function pick(a, b) {
    return a + Math.floor(Math.random() * (b - a + 1));
}
import java.util.Random;
int v = new Random().nextInt(a, b + 1);
import java.util.Random;
int pick(int a, int b){
	return a + new Random().nextInt(b - a + 1);
}
fun pick(a: Int, b: Int): Int {
    return (a..b).random()
}
(defun r (a  b)
(+ a (random (+ 1 (- b a )))))
math.random(a, b)
a+arc4random_uniform(b+1)
rand($a, $b)
uses Math;
var
  _a, _b, _r: Integer;
begin
  _r := RandomRange(_a, _b);
end; 
my ($min, $max) = (5, 25);
my $val = $min + int(rand($max-$min));

import random
random.randint(a,b)
rand(a..b)
use rand::distributions::Distribution;
use rand::distributions::Uniform;
Uniform::new_inclusive(a, b).sample(&mut rand::thread_rng())
extern crate rand;
use rand::distributions::{IndependentSample, Range};
fn pick(a: i32, b: i32) -> i32 {
    let between = Range::new(a, b);
    let mut rng = rand::thread_rng();
    between.ind_sample(&mut rng)
}

import util.Random
a + Random.nextInt(b + 1)
(floor (+ a (* (add1 (- b a)) (random 1.0))))
(+ a (random (add1 (- b a))))

(a to: b) atRandom
New implementation...
< > ⌨
programming-idioms.org 
real :: c
integer :: res

call random_number(c)
res = int((b-a+1)*c)

declare
   subtype Random_Range is Integer range A .. B;
   package Rand is
      new Ada.Numerics.Discrete_Random (Random_Range);
   use Rand;
   Gen    : Generator;
   Result : Random_Range;
begin
   Reset (Gen);
   Result := Random (Gen);
end;
int pick(int a, int b)
{
	int upper_bound = b - a + 1;
	int max = RAND_MAX - RAND_MAX % upper_bound;
	int r;

	do {
		r = rand();
	} while (r >= max);
	r = r % upper_bound;
	return a + r;
}

(+ a (rand-int (- b a)))
std::mt19937 gen;
std::uniform_int_distribution<size_t> uid (a, b);
uid (gen);

Random r = new Random();
return r.Next(a, b + 1);
Random.Shared.Next(a, b + 1)
auto x1 = uniform(a, b+1);
auto x2 = uniform!"[]"(a, b);
int pick(int a, int b) => a + Random().nextInt(b - a + 1);
:crypto.rand_uniform(a, b)
a - 1 + :rand.uniform(b-a+1)
crypto:rand_uniform(A, B)
func pick(a,b int) int {
	return a + rand.Intn(b-a+1)
}
func pick(a, b int) int {
	return a + rand.IntN(b-a+1)
}
let pick (a, b) = randomRIO (a, b) :: IO Integer
 in pick (1, 6) >>= print


function pick(a, b) {
    return a + Math.floor(Math.random() * (b - a + 1));
}
int v = new Random().nextInt(a, b + 1);
int pick(int a, int b){
	return a + new Random().nextInt(b - a + 1);
}
fun pick(a: Int, b: Int): Int {
    return (a..b).random()
}
(defun r (a  b)
(+ a (random (+ 1 (- b a )))))
math.random(a, b)
a+arc4random_uniform(b+1)
rand($a, $b)
var
  _a, _b, _r: Integer;
begin
  _r := RandomRange(_a, _b);
end; 
my ($min, $max) = (5, 25);
my $val = $min + int(rand($max-$min));

random.randint(a,b)
rand(a..b)
Uniform::new_inclusive(a, b).sample(&mut rand::thread_rng())
fn pick(a: i32, b: i32) -> i32 {
    let between = Range::new(a, b);
    let mut rng = rand::thread_rng();
    between.ind_sample(&mut rng)
}

a + Random.nextInt(b + 1)
(floor (+ a (* (add1 (- b a)) (random 1.0))))
(+ a (random (add1 (- b a))))

(a to: b) atRandom