I think having Generator adapted fold functions might help make cleaner code in some cases. (The idea is not new.)

Signatures like:

foldl : (a -> b -> Generator b) -> Generator b -> List a -> Generator b
foldr : (a -> b -> Generator b) -> Generator b -> List a -> Generator b

and an implementation might look something like (with need for improved naming of variables):

random_foldl f start list =
    let
        g : a -> Generator b -> Generator b
        g value generator = generator |> Random.andThen (\ack -> f value ack)
    in
    List.foldl g start list

Do you think the signatures make sense? I guess they might be suitable in Random.List module.

I recently merged to breaking changes, and I want to do a review before releasing a major version. I'm busy with elm-test stuff at the moment so I will need to come back to this in a few days.

i'm using random-extra 2.0.0 compatible version with elm 0.18 but in spite of the package successfully installation and present on the packages folder of elm-stuff the compiler gives an error when trying to import one of the modules, say Random.String for instance, saying it cannot find the module in question. i'm on win10.

the only dependency for random-extra is elm-core, which my project uses version 5.1.1 which fits the spec for random-extra. i have tried to clean exact-dependencies.json with no avail, to reinstall everything from scratch, and also to clone the src locally and add a ref to it on the source-directories section of elm-package but the error persist on either cases. any sugestions are welcome. thx

As of 3.1.0, Random.List.shuffle produces non-uniform shuffle. Shuffling looks uniform(ish) when reverting to 3.0.0. The relevant PRs are #14 and #17 (hi @owanturist!).

@miniBill created an Ellie, which I altered slightly to produce 20 independent rows, each with a List.range 1 50 shuffled. Here are 9 offenders from a single run, with added emphasis for certain regularities:

14 7 6 5 47 29 27 19 4 11 41 17 40 16 38 35 13 3 30 10 26 46 45 12 9 43 2 42 44 1 24 48 34 23 50 22 32 37 28 33 18 25 21 36 49 39 20 31 15 8
11 9 8 5 4 3 1 50 43 26 41 25 22 46 30 49 42 39 15 31 36 40 20 38 6 18 35 37 21 29 44 28 32 14 13 45 12 23 24 34 48 19 7 17 33 16 47 27 10 2
28 44 43 41 40 23 27 25 22 21 19 2 17 26 16 15 14 12 18 39 1 31 10 46 29 5 37 11 33 45 20 13 4 9 3 42 30 7 47 50 48 32 49 36 24 34 35 8 6 38
48 45 44 43 42 41 40 29 9 37 36 7 1 25 35 24 23 20 18 50 17 6 39 4 49 3 28 19 12 34 27 15 5 26 14 2 38 13 22 33 46 16 21 32 31 8 11 10 30 47
16 15 21 14 9 8 5 4 2 40 18 39 38 36 34 33 7 37 47 31 13 19 1 41 11 30 6 3 49 46 43 29 12 28 45 42 22 20 26 32 10 50 24 23 27 48 17 35 25 44
44 43 42 39 35 34 33 32 28 26 29 6 5 25 22 4 38 10 7 2 18 31 46 13 21 20 40 11 41 50 36 9 37 15 14 3 17 8 23 16 12 45 49 1 47 27 19 48 30 24
49 48 47 45 44 39 38 37 31 28 34 27 24 43 23 22 33 21 32 2 20 9 26 14 1 5 41 42 8 13 7 12 4 29 40 19 3 50 36 18 25 15 16 30 11 35 46 6 10 17
36 35 34 33 32 31 29 28 26 25 14 50 24 43 13 21 27 45 3 12 20 11 19 49 10 18 5 47 42 9 48 37 39 8 15 16 17 41 22 7 44 4 30 1 23 38 6 40 46 2
20 18 17 16 30 29 12 21 24 9 34 28 15 14 8 47 32 41 7 23 31 22 6 27 5 3 44 43 2 40 45 35 26 11 46 50 49 10 42 39 37 36 48 1 13 38 33 4 19 25

First, thank you for the hard work and time y'all put in to the this package and thank you for taking the time to consider & respond to this issue.

In the code sample for Random.Extra.andMap, the code sample references person but doesn't explicitly define person. I know that it's probably a type alias somewhere but I don't know if it's an already existing person record or if it's supposed to be a Person constructor.

{-| Turn a list of generators into a generator of lists.
-}
combine : List (Generator a) -> Generator (List a)
combine generators =
    case generators of
        [] ->
            constant []

        g :: gs ->
            Random.map2 (::) g (combine gs)

{-| Start with a list of generators, and turn them into a generator that returns a list.
-}
sequence : List (Generator a) -> Generator (List a)
sequence =
    List.foldr (Random.map2 (::)) (Random.constant [])

The slightly different documentation can also be confusing.

Are there any plans to update this package to Elm 0.19? I'm not actually using it currently, but I will soon need a random list shuffling function. I was pleased to see there was one in this package, but the implementation looked somewhat inefficient so I took a stab at writing my own. The updated implementation is much faster (255% faster on a list of length 10, 438% on a list of length 20, 1196% for 50 and 2654% for 100). I'd be happy to contribute the new implementation to this package, but to make it fully robust it would really need independentSeed in the 0.19 Random package, so I wasn't sure if it was worth making a pull request against a 0.18 version.

Hi there,

I noticed that while there's a shuffle function for Array, I didn't see one for List. I've been sharing a gist I wrote that provides a list shuffling implemention with users on Slack, but I could clean it up and add it to Random.Extra. Is this something you'd be interested in?

The readme makes it sound like the package hasn't been updated since 0.18. You should add something about 0.19 support. :)

This is my elm.json file.

{
    "type": "application",
    "source-directories": [
        "src"
    ],
    "elm-version": "0.19.0",
    "dependencies": {
        "direct": {
            "elm/browser": "1.0.1",
            "elm/core": "1.0.0",
            "elm/html": "1.0.0",
            "elm/random": "1.0.0",
            "elm/svg": "1.0.1",
            "elm-community/random-extra": "3.0.0"
        },
        "indirect": {
            "elm/json": "1.0.0",
            "elm/time": "1.0.0",
            "elm/url": "1.0.0",
            "elm/virtual-dom": "1.0.2"
        }
    },
    "test-dependencies": {
        "direct": {},
        "indirect": {}
    }
}

I try to generate random Array with

faces : Random.Generator (Array.Array Int)
faces =
    Random.Array.array 2 (Random.int 1 6)

This array is accessed with this code only

let
    newFaceOne = Maybe.withDefault 0 (Array.get 0 newFaces)
    newFaceTwo = Maybe.withDefault 0 (Array.get 1 newFaces)
in

When I run make elm allways throws error.

elm make src/Main.elm  --debug
Dependencies loaded from local cache.
Dependencies ready!                
Success! Compiled 1 module.                                          
elm: Map.!: given key is not an element in the map
CallStack (from HasCallStack):
  error, called at ./Data/Map/Internal.hs:610:17 in containers-0.5.11.0-K2TDqgYtGUcKxAY1UqVZ3R:Data.Map.Internal

This error does not happen when I don't use debug. But when I use it happens. Also this happens only when this code is present whit it's alternative Random.list it works just fine. I'm just not sure if this is a good place for this bug report and it is not an error in debugger itself.

Wrote two new combinators that let you create Markov chains with lists

chain : a -> List (a -> Generator a) -> Generator (List a)
repeat : Int -> a -> (a -> Generator a) -> Generator (List a)

Repeat is defined by chain.

If you are interested I could submit a PR.

I ran elm-upgrade on my program and saw this:

WARNING! 1 of your dependencies have not yet been upgraded to 
support Elm 0.18. You can create an issue to request the packages be 
upgraded here:
  - https://github.com/elm-community/random-extra/issues

I'll try to create a PR myself