Random, not so random?

[Kagamin]

Jesse Phillips Wrote:

> void main() {
>     auto arr = [1,2,3,4];
>     auto gen = Random(unpredictableSeed);
> 
>     assert(randomCover(arr,gen) != randomCover(arr,gen));
> 
>     auto result1 = randomCover(arr,gen);
>     auto result2 = randomCover(arr,gen);
>     assert(result1 != result2);

these structs are not equal because they allocated different arrays.

>     auto arr1 = array(randomCover(arr,gen));
>     auto arr2 = array(randomCover(arr,gen));
>     assert(arr1 != arr2);
> 
>     auto str1 = to!string(randomCover(arr,gen));
>     auto str2 = to!string(randomCover(arr,gen));
>     assert(str1 != str2);
> }

these fail because Random is a struct an its state is precisely replicated on copy, so two calls to randomCover accept gen in the same state, so their outputs are identical. All arr1, arr2, str1 and str2 are equivalent.