Joseph Rushton Wakeling:

I think all std.random functions now support a default RNG.


Is the issue is already fixed in std.random you can close it :-)


However, I'd have thought that

    int r = data.sample(1, rndGen).front;

would have been a more efficient way to implement "choice", as it can operate on any input range, as long as it has the .length property; and it ought to be _much_ faster than even a single call to randomCover.

One could always use this as a default option, with a specialization where data is a RandomAccessRange to use the more efficient

    int r = data[uniform!"[)"(0, data.length)];

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


"Strongly pure random generator":
https://d.puremagic.com/issues/show_bug.cgi?id=5249

.front and .popFront at least are pure for _all_ the RNGs currently implemented in std.random2.generator. See e.g.:
https://github.com/WebDrake/std.random2/blob/master/std/random2/generator.d#L266-L272
https://github.com/WebDrake/std.random2/blob/master/std/random2/generator.d#L506-L517
https://github.com/WebDrake/std.random2/blob/master/std/random2/generator.d#L821-L834

Of course this is not strongly pure in line with your request, but it should enable use of these RNGs in many other scenarios where purity is important.

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...


This is a range implementation; there will also be a function implementation, which will probably follow the inefficient Box-Muller variant that uses 2 uniform random variates to generate a single normal variate (as per the example you posted in your feature request).

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


Are the ddocs produced by std.random2 online somewhere?

Bye,
bearophile

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