On Friday, 20 June 2014 at 18:15:49 UTC, Nick Sabalausky wrote:
I'm on the fence:

Pro: Upgrade paths and backwards compatibility are great, especially for Phobos.

Con: If any semantics are changed (default ref/value passing is the only one that comes to mind), then maybe it would mask potential upgrade issues. Breakage would force users to notice the change and (hopefully) deal with it appropriately.

I don't personally see it as a big deal either way, though.

Sorry for taking so long to follow up on this, it's been a busy period ...

Anyway, here's my thinking behind the opCall idea. One of the major shifts of the move to classes is that, suddenly, all of these entities have to be explicitly allocated. That means that there's some measure of responsibility on the library to offer a sane default style of allocation, as appropriate for the expected use-cases and performance requirements.

Now, apart from the random number generators, all of the remaining library functionality already has helper functions which can handle this. Currently they just "new" stuff, but there's no reason this can't be adapted as needed, possibly with the option for some kind of templating around different allocation strategies.

However, RNGs themselves don't have any corresponding helper functions, and manually writing them out would fast become annoying (imagine having to create, say, xorshift, xorshift32, xorshift64, ... etc. as helper functions to create Xorshift, Xorshift32, Xorshift64, etc., instances).

opCall provides a natural way of implementing such construction helper functions that is likely very general purpose, and encouraging it as the default use-case has a further benefit of encouraging the user to always seed their RNGs, if opCall has a form like this:

    static typeof(this) opCall(Seed)(Seed seed)
        return new typeof(this)(seed);

It _could_ be done as a temporary measure, deprecated from the start, to allow drop-in replacement but encourage appropriate adaptation. But it could also be a way to serve the user with sensible default allocation strategies that minimize the potential performance impacts of the switch to classes.

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