• harfel (8/8) Dec 17 2018 I am looking for a way to serialize/deserialize the state of the
• Neia Neutuladh (9/16) Dec 17 2018 The .tupleof field allows you to access private members. This behavior
• Steven Schveighoffer (7/28) Dec 18 2018 std.traits.hasIndirections

harfel <dadapapa gmail.com> writes:

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!

Neia Neutuladh <neia ikeran.org> writes:

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.

Steven Schveighoffer <schveiguy gmail.com> writes:

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