How do I generate random numbers in Dart

Question

How do I generate random numbers using Dart

User · Answer

Just wrote this little class for generating Normal Random numbers... it was a decent starting point for the checking I need to do. (These sets will distribute on a "bell" shaped curve.) The seed will be set randomly, but if you want to be able to re-generate a set you can just pass some specific seed and the same set will generate.

Have fun...

class RandomNormal {
  num     _min, _max,  _sum;
  int     _nEle, _seed, _hLim;
  Random  _random;
  List    _rNAr;

  //getter
  List get randomNumberAr => _rNAr;

  num _randomN() {
    int r0 = _random.nextInt(_hLim);
    int r1 = _random.nextInt(_hLim);
    int r2 = _random.nextInt(_hLim);
    int r3 = _random.nextInt(_hLim);

    num rslt = _min + (r0 + r1 + r2 + r3) / 4000.0;  //Add the OS back in...
    _sum += rslt; //#DEBUG ONLY
    return( rslt );
  }

  RandomNormal(this._nEle, this._min, this._max, [this._seed = null]) {
    if (_seed == null ) {
      Random r = new Random();
      _seed    = r.nextInt(1000);
    }
    _hLim   = (_max - _min).ceil() * 1000;
    _random = new Random(_seed);
    _rNAr   = [];
    _sum    = 0;//#DEBUG ONLY

    h2("RandomNormal with k: ${_nEle}, Seed: ${_seed}, Min: ${_min}, Max: ${_max}");//#DEBUG ONLY
    for(int n = 0; n < _nEle; n++ ){
      num randomN = _randomN();
      //p("randomN  = ${randomN}");
      LIST_add( _rNAr, randomN );
    }

    h3("Mean = ${_sum/_nEle}");//#DEBUG ONLY
  }
}


new RandomNormal(1000, 80, 120);
new RandomNormal(1000, 80, 120);
new RandomNormal(1000, 80, 120);
new RandomNormal(1000, 80, 120);
new RandomNormal(1000, 80, 120);
new RandomNormal(1000, 80, 120);
new RandomNormal(1000, 80, 120);

Then you can just use it like this to check the mean of sets of 1000 nums generated between a low and high limit. The values are stored in the class so they can be accessed after instantiation.

_swarmii

User · Answer

its worked for me  new Random   nextInt 100      MAX   number  it will give 0 to 99 random number  Eample    import  dart math   int MAX   100  print new Random   nextInt MAX

User · Answer

Not able to comment because I just created this account  but I wanted to make sure to point out that  eggrobot78 s solution works  but it is exclusive in dart so it doesn t include the last number  If you change the last line to  r   min   rnd nextInt max - min   1     then it should include the last number as well   Explanation   max   5  min   3  Random rnd   new Random    r   min   rnd nextInt max - min     max - min is 2   nextInt is exclusive so nextInt will return 0 through 1   3 is added so the line will give a number between 3 and 4   if you add the    1  then it will return a number between 3 and 5

User · Answer

Let me solve this question with a practical example in the form of a simple dice rolling app that calls 1 of 6 dice face images randomly to the screen when tapped  first declare a variable that generates random numbers  don t forget to import dart math   Then declare a variable that parses the initial random number within constraints between 1 and 6 as an Integer  Both variables are static private in order to be initialized once This is is not a huge deal but would be good practice if you had to initialize a whole bunch of random numbers  static var  random   new Random    static var  diceface    random nextInt 6   1    Now create a Gesture detection widget with a ClipRRect as a child to return one of the six dice face images to the screen when tapped  GestureDetector            onTap                   setState                     diceface    rnd nextInt 6   1                                          child  ClipRRect              clipBehavior  Clip hardEdge              borderRadius  BorderRadius circular 100 8                 child  Image                  image  AssetImage  images diceface  diceface png                    fit  BoxFit cover                                           A new random number is generated each time you tap the screen and that number is referenced to select which dice face image is chosen  I hoped this example helped    Dice rolling app using random numbers in dart

User · Answer

A secure random API was just added to dart math  new Random secure        dart math     Random added a secure constructor returning a cryptographically secure     random generator which reads from the entropy source provided by the     embedder for every generated random value    which delegates to window crypto getRandomValues   in the browser and to the OS  like urandom on the server

User · Answer

You can achieve it via Random class object random nextInt max   which is in dart math library  The nextInt   method requires a max limit  The random number starts from 0 and the max limit itself is exclusive   import  dart math   Random random   new Random    int randomNumber   random nextInt 100      from 0 upto 99 included   If you want to add the min limit  add the min limit to the result  int randomNumber   random nextInt 90    10     from 10 upto 99 included

User · Answer

If you need cryptographically-secure random numbers  e g  for encryption   and you re in a browser  you can use the DOM cryptography API   int random       final ary   new Int32Array 1     window crypto getRandomValues ary     return ary 0       This works in Dartium  Chrome  and Firefox  but likely not in other browsers as this is an experimental API

User · Answer

use this library http   dart googlecode com svn branches bleeding edge dart lib math random dart provided a good random generator which i think will be included in the sdk soon hope it helps

User · Answer

try this  you can control the min max value   import  dart math    void main      random min  max       var rn   new Random        return min   rn nextInt max - min         print random 5 20       Output   19  6  15

User · Answer

Use Dart Generators  that is used to produce a sequence of number or values   main            print  quot Sequence Number quot           oddnum 10  forEach print              Iterable lt int gt  oddnum int num  sync        int k num       while k gt  0          if k 2  1           yield k                 k--

User · Answer

Use Random class from dart math   import  dart math    main       var rng   new Random      for  var i   0  i  lt  10  i          print rng nextInt 100            This code was tested with the Dart VM and dart2js  as of the time of this writing

User · Answer

For me the easiest way is to do   import  dart math   Random rnd   new Random    r   min   rnd nextInt max - min     where min and max should be specified    Thanks to  adam-singer explanation in here

User · Answer

An alternative solution could be using the following code DRandom  This class should be used with a seed  It provides a familiar interface to what you would expect in  NET  it was ported from mono s Random cs  This code may not be cryptography safe and has not been statistically tested

User · Answer

Here s a snippet for generating a list of random numbers  import  dart math    main       var rng   new Random      var l   new List generate 12        gt  rng nextInt 100        This will generate a list of 12 integers from 0 to 99  inclusive

[random] How do I generate random numbers in Dart?

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