saving std.random RNG state

[Steven Schveighoffer]

On 12/17/18 8:18 PM, Neia Neutuladh wrote:
> On Mon, 17 Dec 2018 22:20:54 +0000, harfel wrote:
>> I am looking for a way to serialize/deserialize the state of the
>> std.random.Random number generator, ideally using orange
>> (https://github.com/jacob-carlborg/orange) or another serialization
>> library. From looking at the module source code, I understand how to
>> seed a random number generator with the state of another, but I do find
>> a way to access the RNG's state, since it is hidden away in a private
>> attribute. What is the recommended solution for this? Thanks in advance!
> 
> The .tupleof field allows you to access private members. This behavior
> might eventually change, but probably not without a long deprecation
> period.
> 
> If the struct stores everything by value:
> 
>      cast(ubyte[])&rng[0..1];
> 
> If you have typeinfo available, you can check if the thing has pointers
> with `(typeof(rng).flags & 1) == 0`. There's probably an equivalent in
> std.traits that works at compile time.
> 

std.traits.hasIndirections

https://dlang.org/phobos/std_traits.html#hasIndirections

In terms of storing the state, I find generally just using the same seed 
is best, but I can see use cases for storing the state for usage 
elsewhere. I don't see a better way than using a ubyte[] cast.

-Steve