Xcode 11 • Swift 5.1 extension Collection { func choose(_ n: Int) -> ArraySlice<Element> { shuffled().prefix(n) } } Playground testing var alphabet = [“A”,”B”,”C”,”D”,”E”,”F”,”G”,”H”,”I”,”J”,”K”,”L”,”M”,”N”,”O”,”P”,”Q”,”R”,”S”,”T”,”U”,”V”,”W”,”X”,”Y”,”Z”] let shuffledAlphabet = alphabet.shuffled() // “O”, “X”, “L”, “D”, “N”, “K”, “R”, “E”, “S”, “Z”, “I”, “T”, “H”, “C”, “U”, “B”, “W”, “M”, “Q”, “Y”, “V”, “A”, “G”, “P”, “F”, “J”] … Read more
var min = -10; var max = 10; // and the formula is: var random = Math.floor(Math.random() * (max – min + 1)) + min;
Here’s a useful trick 🙂 function randomWithProbability() { var notRandomNumbers = [1, 1, 1, 1, 2, 2, 2, 3, 3, 4]; var idx = Math.floor(Math.random() * notRandomNumbers.length); return notRandomNumbers[idx]; }
function random_rgba() { var o = Math.round, r = Math.random, s = 255; return ‘rgba(‘ + o(r()*s) + ‘,’ + o(r()*s) + ‘,’ + o(r()*s) + ‘,’ + r().toFixed(1) + ‘)’; } var color = random_rgba(); g.fillStyle = color; g.strokeStyle = color; FIDDLE
The order_by(‘?’)[:2] solution suggested by other answers is actually an extraordinarily bad thing to do for tables that have large numbers of rows. It results in an ORDER BY RAND() SQL query. As an example, here’s how mysql handles that (the situation is not much different for other databases). Imagine your table has one billion … Read more
The point of having a seed_seq is to increase the entropy of the generated sequence. If you have a random_device on your system, initializing with multiple numbers from that random device may arguably do that. On a system that has a pseudo-random number generator I don’t think there is an increase in randomness, i.e. generated … Read more
Simply use rand.Float64() to get a random number in the range of [0..1), and you can map (project) that to the range of [min..max) like this: r := min + rand.Float64() * (max – min) And don’t create a new rand.Rand and / or rand.Source in your function, just create a global one or use … Read more
As explained in the rand 0.5.0 docs, gen_ascii_chars is deprecated and you should use sample_iter(&Alphanumeric) instead. use rand::{distributions::Alphanumeric, Rng}; // 0.8 fn main() { let s: String = rand::thread_rng() .sample_iter(&Alphanumeric) .take(7) .map(char::from) .collect(); println!(“{}”, s); }
Vectorized solution with rand+argsort trick We could generate unique indices along the specified axis and index into the the input array with advanced-indexing. To generate the unique indices, we would use random float generation + sort trick, thus giving us a vectorized solution. We would also generalize it to cover generic n-dim arrays and along … Read more