C#•16mo ago

✅ Interesting uses of yield return

I recently needed to generate an arbitrary number of unique random numbers, and after a little thinking I found I could get a really elegant solution by using yield return to generate an infinite stream of ints. This made me realise I basically never use this language feature and there's probably a lot of cool applications for it I'm missing. Any tricks/interesting patterns you've written with it?

16 Replies

Becquerel•16mo ago

for anyone interested, what I did was this:

    private IEnumerable<int> GetRandom(int max)
    {
        while (true)
        {
            yield return Random.Shared.Next(max);
        }
    }

var randoms = GetRandom(someNumber)
.Distinct()
.Take(amount)
.ToList();

    private IEnumerable<int> GetRandom(int max)
    {
        while (true)
        {
            yield return Random.Shared.Next(max);
        }
    }

var randoms = GetRandom(someNumber)
.Distinct()
.Take(amount)
.ToList();

ero•16mo ago

(basically just)

Enumerable.Range(0, amount)
.Select(_ => Random.Shared.Next(someNumber))
.Distinct()
.ToList();

Enumerable.Range(0, amount)
.Select(_ => Random.Shared.Next(someNumber))
.Distinct()
.ToList();

Kesa•16mo ago

yield return is indeed very useful

ero•16mo ago

I'd say it's rarely used in the way they're using it here

Becquerel•16mo ago

damn, I should have thought of that!

Thinker•16mo ago

What they're most useful for is probably returning collections of things where each item is potentially computationally intensive and where it's useful to let the caller decide how many items it needs. It's like a task in the sense that the caller can decide to interrupt the enumeration (and therefore execution of the method) at any time. (hell, Unity uses yield for its async stuff)

Anton•16mo ago

this can give you fewer numbers than amount I suppose there's no built-in infinite range in linq

Cattywampus•16mo ago

it's not true async btw coffeevee

ero•16mo ago

Yeah I noticed as soon as I posted. Would this be a worthwhile proposal?

Anton•16mo ago

what do you mean?

ero•16mo ago

Propose an infinite range in Linq to dotnet/runtime

Anton•16mo ago

I guess it's no different than introducing ISystemClock or similar helpers that you can code in 3 lines

canton7•16mo ago

Why do you need an infinite range thing? If you keep asking OP's GetRandom for the next value, it will keep giving you one -- an infinite stream of random values. No need to generate an infinite range and then map each element to a random value, or something

Becquerel•16mo ago

i will note one little discrepancy in my original code i'm curious about if the amount you .Take() is greater than max, the program will deadlock eventually i figured out this was because it's obviously impossible to have, say, 50 unique numbers less than 34 but i was surprised i didn't get an exception anywhere i don't know if there's an intelligent way to order the LINQ methods so that kind of subtle bug is more obvious think

canton7•16mo ago

Hmm, I don't think so. The knowledge required to detect that problem is kinda spread out over the whole pipeline.

Becquerel•16mo ago

RIP

Gaming

Programming

✅ Interesting uses of yield return