Random number generator - a class or a record?

[vasslitvinov]

Should the random generator provided by the standard library be:

• a class (which it currently is), or
• a record, or
• a record-wrapped class?

Issues to consider:

• What do we want to be the initialization/assignment semantics -- duplicating the reference or copying? Many of our standard data structures perform copying. For a random number generator copying means starting at the same place. Whatever approach we take, semantics of when copies are made should be obvious to user.

• What is the desired behavior for remote accesses? For example, what should fillRandom() do? Currently it creates a per-locale version.

• If it is a class, it is easy for nilability or ownership issues to start biting the user. Although nilability is unlikely to become an issue because the user variable holding the class will likely be non-nilable.

• If it is a record-wrapped class, what should be the ownership policy? This perhaps comes back to the above question on copy semantics. Having just a record seems simpler conceptually, easier to use.

• If it is a record-wrapped class, how much additional complexity does this introduce for the implementer of another generator?

[vasslitvinov]

The first step is to make a prototype solution, once the Random module has been simplified to provide just a single type of random number generator. See also #19601

[bradcray]

I think it should be a record from the user's perspective, and whether or not it wraps a class is our business as the implementers.

[mppf]

IMO it can and should be a plain record. The state is relatively small and can just be copied around. Also, it makes intuitive sense to me, if I copy an RNG, that I can advance each copy independently.

[lydia-duncan]

Random is no longer intended for 2.0, removing the tag