On Sunday, 23 March 2014 at 10:15:32 UTC, bearophile wrote:
> Is the issue is already fixed in std.random you can close it :-)

Well, your request for a "choice" method is still open ... :-)

> The best thing is to add an efficient choice() function, so no efficiency mistake happens :-)

Sure, I'm simply raising a couple of simple internal implementations that could be used for an effective first draft of that function.

> So you are saying that those RNGs are already weakly pure and they can't become strongly pure because they take the engine as mutable class reference. And even if you design a very small random engine that can be created every time you call a random generator, the API of all the random functions is not compatible with it. So it's not a simple problem...

I think I need to make some detailed research into how Haskell and other functional languages handle randomness before commenting here.  What it does seem to me at this stage is that while a weakly pure range-based RNG is readily possible (as implemented in std.random2.generator now), I'm not sure that the range-based approach typical of Phobos plays nicely with strong purity where random number generation is concerned.

> A possibility is to also add a less precise (more approximate) but faster function implementation.

Again, this is something I'll look into.  I need to re-read the paper on gaussian-distribution algorithms that I linked to earlier in this thread, but my recollection is that the speed/precision tradeoff is something of a false dichotomy given the algorithms out there now; so a good range-based solution (which stores internal state) will probably be able to provide high-quality normal variates faster than a low-quality, purely function-based implementation.

> Are the ddocs produced by std.random2 online somewhere?

Not yet.  I can make that happen :-)

On Thursday, 20 March 2014 at 00:09:51 UTC, bearophile wrote:
> Do you have a simple but very fast function that generates uniforms in [0.0, 1.0]? :-)

On that note: https://github.com/D-Programming-Language/phobos/pull/2050

Hope you don't mind me jumping ahead of your existing PR on this -- it's been inactive so I didn't know if you were planning on following up.  I'd be very happy to see you take what's good from the above into your own patchset, we need to land a contribution from you in Phobos :-)

Joseph Rushton Wakeling:

> Hope you don't mind me jumping ahead of your existing PR on this -- it's been inactive so I didn't know if you were planning on following up.

I don't mind, I am happy :-) Thank you for adding a sorely needed function.
The useless patch I opened should be closed.

Bye,
bearophile

On Tuesday, 25 March 2014 at 00:08:27 UTC, bearophile wrote:
> I don't mind, I am happy :-) Thank you for adding a sorely needed function.

You are very kind, and far too modest. :-)

On Tuesday, 25 March 2014 at 00:08:27 UTC, bearophile wrote:
> I don't mind, I am happy :-) Thank you for adding a sorely needed function.

It's been merged :-)